Terminal device, base station device, and communication method

ABSTRACT

To efficiently control a cell by using a non-allocated frequency band or a shared frequency band. The terminal device includes a reception unit configured to receive a PDCCH, a transmission unit configured to transmit a PUSCH in a serving cell, and a CCA check unit configured to perform either first LBT for performing a CCA check a number of times based on a random number before a subframe for which a transmission of the PUSCH is indicated or second LBT for performing a CCA check only once. The terminal device switches between the first LBT and the second LBT, based on a prescribed condition.

TECHNICAL FIELD

Embodiments of the present invention relate to a technique of a terminaldevice, a base station device, and a communication method that enableefficient communication.

BACKGROUND ART

The 3rd Generation Partnership Project (3GPP), which is astandardization project, standardized the Evolved Universal TerrestrialRadio Access (hereinafter, referred to as E-UTRA), in which high-speedcommunication is realized by adopting an Orthogonal Frequency-DivisionMultiplexing (OFDM) communication scheme and flexible scheduling using aunit of prescribed frequency and time called resource block.

Moreover, the 3GPP discusses Advanced E-UTRA, which realizeshigher-speed data transmission and has upper compatibility with E-UTRA.E-UTRA relates to a communication system based on a network in whichbase station devices have substantially the same cell configuration(cell size); however, regarding Advanced E-UTRA, discussion is made on acommunication system based on a network (different-type radio network,Heterogeneous Network) in which base station devices (cells) havingdifferent configurations coexist in the same area. In this regard,E-UTRA is also referred to as “LTE (Long Term Evolution)”, and AdvancedE-UTRA is also referred to as “LTE-Advanced”. Furthermore, LTE may be acollective name including LTE-Advanced.

A Carrier Aggregation (CA) technique and a Dual Connectivity (DC)technique are specified, in which, in a communication system where cells(macro cells) having large cell radii and cells (small cells) havingsmaller cell radii than those of the macro cells coexist as in aheterogeneous network, a terminal device performs communication byconnecting to a macro cell and a small cell simultaneously (NPL 1).

Meanwhile, NPL 2 studies Licensed-Assisted Access (LAA). According toLAA, a non-allocated frequency band (Unlicensed spectrum) used by awireless Local Area Network (LAN) is used as LTE. More specifically, thenon-allocated frequency band is configured as a secondary cell(secondary component carrier). Connection, communication, and/or aconfiguration of the secondary cell(s) used as LAA are assisted by aprimary cell (primary component carrier) configured to an allocatedfrequency band (Licensed spectrum). LAA widens a frequency band that isavailable for LTE, and thus wide band transmission is enabled. In thisregard, LAA is used in a shared frequency band (shared spectrum) sharedbetween prescribed operators.

CITATION LIST Non-Patent Document

[NON-PATENT DOCUMENT 1] NPL 1: 3rd Generation Partnership Project;Technical Specification Group Radio Access Network; Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical layer procedures (Release12), 3GPP TS 36.213 V12.4.0 (2014-12).

[NON-PATENT DOCUMENT 2] NPL 2: 3rd Generation Partnership Project;Technical Specification Group Radio Access Network; Study onLicensed-Assisted Access to Unlicensed Spectrum; (Release 13), 3GPP TR36.889 V1.0.1 (2015-6).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

According to LAA, in a case that the non-allocated frequency band or theshared frequency band is used, the frequency band is shared betweenother systems and/or other operators. However, LTE is designed assuminguse in an allocated frequency band or a non-shared frequency band.Therefore, the LTE in the related art may not be used in thenon-allocated frequency band or the shared frequency band.

Some aspects of the present invention have been made in view of theabove-described respects, and an object of the present invention is toprovide a terminal device, a base station device, and a communicationmethod that allow efficient control of a cell using a non-allocatedfrequency band or a shared frequency band.

Means for Solving the Problems

(1) In order to accomplish the above-described object, according to someaspects of the present invention, the following measures are provided.In other words, a terminal device according to an aspect of the presentinvention includes a reception unit configured to receive a PDCCH, atransmission unit configured to transmit a PUSCH in a serving cell, anda CCA check unit configured to perform either first LBT for performing aCCA check a number of times based on a random number before a subframefor which a transmission of the PUSCH is indicated or second LBT forperforming a CCA check only once. The terminal device switches betweenthe first LBT and the second LBT, based on a prescribed condition.

(2) Moreover, a base station device according to an aspect of thepresent invention is a base station device for communicating with aterminal device, the base station device including a transmission unitconfigured to transmit a PDCCH, and a reception unit configured toreceive a PUSCH in a serving cell. The base station device is configuredto instruct the terminal device to switch between first LBT forperforming a CCA check a number of times based on a random number beforea subframe for which a transmission of the PUSCH is indicated, andsecond LBT for performing a CCA check only once.

(3) Moreover, a communication method according to an aspect of thepresent invention is a communication method used by a terminal device,the communication method including: receiving a PDCCH; transmitting aPUSCH in a serving cell; and performing either first LBT for performinga CCA check a number of times based on a random number before a subframefor which a transmission of the PUSCH is indicated or second LBT forperforming a CCA check only once, the communication method switchesbetween the first LBT and the second LBT, based on a prescribedcondition.

(4) Moreover, a communication method according to an aspect of thepresent invention is a communication method used by a base stationdevice for communicating with a terminal device, the communicationmethod including: transmitting a PDCCH; and receiving a PUSCH in aserving cell. The communication method includes instructing the terminaldevice to switch between first LBT for performing a CCA check a numberof times based on a random number before a subframe for which atransmission of the PUSCH is indicated, and second LBT for performing aCCA check only once.

Effects of the Invention

According to some aspects of the present invention, in a radiocommunication system, in which a base station device and a terminaldevice communicate, transmission efficiency is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a downlink radio frameconfiguration according to a present embodiment.

FIG. 2 is a diagram illustrating an example of an uplink radio frameconfiguration according to the present embodiment.

FIG. 3 is a schematic diagram illustrating an example of a blockconfiguration of a base station device 2 according to the presentembodiment.

FIG. 4 is a schematic diagram illustrating an example of a blockconfiguration of a terminal device 1 according to the presentembodiment.

FIG. 5 is a diagram illustrating an example of a downlink signalconfiguration according to the present embodiment.

FIG. 6 is a diagram illustrating an example of a procedure of CCA for adownlink transmission according to a present embodiment.

FIGS. 7A to 7C are diagrams illustrating an example of a relationshipbetween an interval, between a downlink transmission and an uplinktransmission, and types of CCA according to the present embodiment.

FIG. 8 is a diagram illustrating an example of a procedure of CCA for anuplink transmission according to the present embodiment.

FIG. 9 is a diagram illustrating an example of a procedure of CCA for anuplink transmission according to the present embodiment.

FIG. 10 is a diagram illustrating an example of frequency multiplexingof a physical uplink shared channel according to the present embodiment.

FIG. 11 is a diagram illustrating an example of CCA for an uplinktransmission according to the present embodiment.

FIG. 12 is a diagram illustrating an example of CCA for an uplinktransmission according to the present embodiment.

FIG. 13 is a diagram illustrating an example of CCA for an uplinktransmission according to the present embodiment.

FIG. 14 is a diagram illustrating an example of CCA for an uplinktransmission according to the present embodiment.

FIG. 15 is a diagram illustrating an example of a procedure of CCA foran uplink transmission according to the present embodiment.

MODE FOR CARRYING OUT THE INVENTION

First Embodiment

A first embodiment of the present invention will be described below. Adescription will be given by using a communication system (cellularsystem) in which a base station device (base station, NodeB, or eNodeB(eNB)) and a terminal device (terminal, mobile station, a user device,or User equipment (UE)) communicate in a cell.

A physical channel and a physical signal substantially used in EUTRA andAdvanced EUTRA will be described. The “channel” refers to a medium usedto transmit a signal, and the “physical channel” refers to a physicalmedium used to transmit a signal. In the present embodiment, thephysical channel may be used synonymously with “signal.” In the futureEUTRA and Advanced EUTRA, the physical channel may be added or itsconstitution and format type may be changed or added; however, thedescription of the present embodiment will not be affected even if thechannel is changed or added.

In EUTRA and Advanced EUTRA, scheduling of a physical channel or aphysical signal is managed by using a radio frame. One radio frame is 10ms in length, and one radio frame is constituted of 10 subframes. Inaddition, one subframe is constituted of two slots (i.e., one subframeis 1 ms in length, and one slot is 0.5 ms in length). Moreover,scheduling is managed by using a resource block as a minimum unit ofscheduling for allocating a physical channel. The “resource block” isdefined by a given frequency domain constituted of a set of multiplesubcarriers (e.g., 12 subcarriers) on a frequency axis and a domainconstituted of a specific transmission time slot (one slot).

In the EUTRA and Advanced EUTRA, a frame structure type is defined.Frame structure type 1 is applicable to Frequency Division Duplex (FDD).Frame structure type 2 is applicable to Time Division Duplex (TDD).

FIG. 1 is a diagram illustrating an example of a downlink radio frameconfiguration according to the present embodiment. In the downlink, anOFDM access scheme is used. Transmission of a downlink signal and/or ona downlink physical channel in the downlink is referred to as a downlinktransmission. In the downlink, a PDCCH, an EPDCCH, a Physical DownlinkShared CHannel (PDCCH), and the like are allocated. A downlink radioframe is constituted by a downlink Resource Block (RB) pair. Thisdownlink RB pair is a unit for allocation of a downlink radio resourceand the like and is based on the frequency band of a predefined width(RB bandwidth) and a time duration (two slots=1 subframe). Each of thedownlink RB pairs is constituted of two downlink RBs (RB bandwidth×slot)that are contiguous in time domain. Each of the downlink RBs isconstituted of 12 subcarriers in frequency domain. In the time domain,the downlink RB is constituted of seven OFDM symbols in a case that anormal cyclic prefix (CP) is added, while the downlink RB is constitutedof six OFDM symbols in a case that a cyclic prefix that is longer thanthe normal cyclic prefix is added. A region defined by a singlesubcarrier in the frequency domain and a single OFDM symbol in the timedomain is referred to as “Resource Element (RE)”. A physical downlinkcontrol channel is a physical channel on which downlink controlinformation such as a terminal device identifier, physical downlinkshared channel scheduling information, physical uplink shared channelscheduling information, and a modulation scheme, coding rate, andretransmission parameter are transmitted. Note that although a downlinksubframe in a single Component Carrier (CC) is described here, adownlink subframe is defined for each CC and downlink subframes areapproximately synchronized between the CCs.

In the downlink, synchronization signals are assigned. Thesynchronization signals are used to adjust timings for downlink signalsand/or channels mainly between a base station device transmittingdownlink signals and/or channels and a terminal device receivingdownlink signals and/or channels. Specifically, at the terminal device,synchronization signal is used to adjust timings of receiving radioframes or subframes, or OFDM symbols. At the terminal device, asynchronization signal is also used to detect a center frequency of acomponent carrier. At the terminal device, a synchronization signal isalso used to detect the CP length of an OFDM symbol. At the terminaldevice, a synchronization signal is also used to identify the cell (basestation device) from which the synchronization signal has beentransmitted. In other words, at the terminal device, a synchronizationsignal is used to detect a cell identity of the cell from which thesynchronization signal has been transmitted. Note that, at the terminaldevice, a synchronization signal may be used to perform Automation GainControl (AGC). Note that, at the terminal device, a synchronizationsignal may be used to adjust a timing of processing symbol to be usedfor Fast Fourier Transform (FFT). Note that, at the terminal device, asynchronization signal may be used to calculate Reference SignalReceived Power (RSRP). Note that a synchronization signal may be used tosecure a channel on which the synchronization signal is to betransmitted.

A primary synchronization signal (first primary synchronization signal)and a secondary synchronization signal (first secondary synchronizationsignal) are transmitted on the downlink to promote cell searches. Cellsearch is a procedure performed by the terminal device to acquire timeand frequency synchronization with the cell to detect a physical layercell ID of the cell. E-UTRA cell search supports a flexible and generaltransmission bandwidth corresponding to six or more resource blocks.

A specific example of assignment (arrangement, mapping) of the primarysynchronization signal and the secondary synchronization signal will bedescribed. k is defined as a frequency domain, and l is identified as anindex specifying a resource element in the time domain. Here. N_(RB)^(DL) denotes the number of resource blocks specified based onconfiguration information about the downlink bandwidth, N_(sc) ^(RB)denotes a frequency domain resource block size corresponding to thenumber of subcarriers per resource block, and N_(symb) ^(DL) denotes thenumber of OFDM symbols per downlink slot. Here, a_(k,l) denotes a symbolin a resource element (k, l), d denotes a sequence, and n takes a valuefrom 0 to 2N_(M)-1. Moreover, mod denotes a function representing aremainder, and A mod B denotes a remainder in a case that A is dividedby B. Here, for the primary synchronization signal and the secondarysynchronization signal, N_(M) is 31. Here, for the primarysynchronization signal and the secondary synchronization signal, h is 1.

The Primary Synchronization Signal (PSS) and the SecondarySynchronization Signal (SSS) illustrated in FIG. 1 are transmitted using62 subcarriers (62 resource elements) around a center frequencyregardless of the downlink bandwidth (a system bandwidth of thedownlink, a downlink transmission bandwidth). A direct-currentsubcarrier (DC subcarrier) corresponding to the center of thesubcarriers within the system bandwidth is not used as the primarysynchronization signal or the secondary synchronization signal. Fivesubcarriers (five resource elements) at each of opposite ends of each ofthe primary synchronization signal and the secondary synchronizationsignal are reserved and not used for transmission of the primarysynchronization signal or the secondary synchronization signal. Theresource elements including the five resource elements at each end inaddition to the above-described 62 resource elements are referred to asthe primary synchronization signal and the secondary synchronizationsignal.

The primary synchronization signal is generated based on a Zadoff-Chusequence (ZC sequence) in the frequency domain. N_(ZC) denotes asequence length of the Zadoff-Chu sequence, and u denotes a root index(Zadoff-Chu root sequence index). The primary synchronization signal isgenerated based on three types of root indices. Each of the root indicesis associated with three specific identifiers derived from the cellidentity (cell ID, physical-layer cell identity). In frame structuretype 1, the primary synchronization signal is assigned to the last OFDMsymbols of slot 0 (i.e., the first slot of subframe 0) and slot 10(i.e., the first slot of subframe 5). In frame structure type 2, theprimary synchronization signal is assigned to the third OFDM symbols ofthe first slots of subframes 1 and 6.

The secondary synchronization signal is defined by a combination of twosequences each having a length of 31. A sequence used for the secondarysynchronization signal is obtained by interleaving and combining the twosequences each having a length of 31. The sequence resulting from thecombining is scrambled with a scramble sequence provided by the primarysynchronization signal. The sequence having a length of 31 is generatedbased on an M sequence. The sequence having a length of 31 is generatedbased on 168 specific physical layer cell identity groups derived fromthe cell identity. The scramble sequence provided by the primarysynchronization signal is an M sequence generated based on threespecific identifiers. Mapping of the sequence of the secondarysynchronization signal on the resource elements depends on a framestructure. In frame structure type 1, the secondary synchronizationsignal is assigned to the second OFDM symbol from the last OFDM symbolof slot 0 (i.e., the first slot of subframe 0 ) and slot 10 (i.e., thefirst slot of subframe 5 ). In frame structure type 2, the secondarysynchronization signal is assigned to the last OFDM symbols of slot 1(i.e., the second slot of subframe 0) and slot 11 (i.e., the second slotof subframe 5).

Although not illustrated here, a physical broadcast information channelmay be allocated and a downlink Reference Signal (RS) may be assigned,to a downlink subframe. Examples of a downlink reference signal are aCell-specific RS (CRS), which is transmitted through the sametransmission port as that for a PDCCH, a Channel State Information RS(CSI-RS, non-zero power CSI-RS, NLP CSI-RS), which is used to measureChannel State Information (CSI), a terminal-specific RS (UE-specific RS(URS)), which is transmitted through the same transmission port as thatfor one or some PDSCHs, and a Demodulation RS (DMRS), which istransmitted through the same transmission port as that for an EPDCCH.Moreover, carriers on which no CRS is mapped may be used. In this case,a similar signal (referred to as “enhanced synchronization signal”) to asignal corresponding to one or some transmission ports (e.g., onlytransmission port 0) or all the transmission ports for the CRSs can beinserted into one or some subframes (e.g., the first and sixth subframesin the radio frame) as time and/or frequency tracking signals. Theterminal-specific reference signals transmitted at the same transmissionport as part of PDSCHs are also referred to as terminal-specificreference signals or DMRSs associated with PDSCHs. The demodulationreference signals transmitted at the same transmission port as theEPDCCHs are also referred to as DMRSs associated with the EPDCCHs

Although not illustrated here, in the downlink subframe, Zero PowerCSI-RS (ZP CSI-RS) mostly used for rate matching of the PDSCH, which istransmitted simultaneously with the downlink subframe, and CSIInterference Management (CSI-IM) mostly used for interferencemeasurement of channel state information may be mapped. The zero powerCSI-RS and the CSI-IM may be arranged on resource elements where thenon-zero power CSI-RS can be mapped. The CSI-IM may be configured tooverlap the non-zero CSI-RS.

Although not illustrated, Discovery Signals (DSs) may be arranged indownlink subframes. In a certain cell, a DS (DS Occasion) is constitutedof a time period (DS period) of a prescribed number of contiguoussubframes. The prescribed number is one to five according to MD (Framestructure type 1) and two to five according to TDD (Frame structure type2). The prescribed number is configured by the RRC signaling. Theterminal device is configured to have an occasion when the DS period ismeasured. The configuration of the occasion when the DS period ismeasured is also referred to as a Discovery signals Measurement TimingConfiguration (DMTC). The occasion (DMTC Occasion) when the terminaldevice measures the DS period is configured by an occasion correspondingto 6 ms (six subframes). The terminal assumes that the DS is transmitted(is mapped or occurs) per subframe configured by a parameterdmtc-Periodicity configured by the RRC signaling. The terminal assumes apresence of the DS configured to include following signals in downlinksubframes.

(1) A CRS of antenna port 0 in a DwPTS of all downlink subframes and allspecial subframes in the DS period.

(2) A PSS in a first subframe of the DS period according to FDD, A PSSin the second subframe of the DS period according to TDI).

(3) A SSS in the first subframe of the DS period.

(4) A non-zero power CSI-RS in a zero or more subframes of the DS periodThis non-zero power CSI-RS is configured by the RRC signaling.

The terminal performs measurements based on the configured DS. Themeasurements are performed by using the CRS of the DS or the non-zeropower CSI-RS of the DS. The configuration related to the DS canconfigure multiple non-zero power CSI-RSs.

FIG. 2 is a diagram illustrating an example of an uplink radio frameconfiguration according to the present embodiment. An SC-FDMA scheme isused in the uplink. Transmission of an uplink signal and/or on an uplinkphysical channel in the uplink is referred to as an uplink transmission.That is, the uplink transmission can be rephrased as transmission of aPUSCH. In the uplink, a Physical Uplink Shared CHannel (PUSCH), a PUCCH,and the like are allocated. An uplink reference signal is assigned toone or some of PUSCHs and PUCCHs. An uplink radio frame is constitutedof uplink RB pairs. This uplink RB pair is a unit for allocation ofuplink radio resources and the like and is constituted by the frequencyband of a predefined width (RB bandwidth) and a predetermined timeduration (two slots=1 subframe). Each of the uplink RB pairs isconstituted of two uplink RBs (RB bandwidth×slot) that are contiguous inthe time domain. Each of the uplink RB is constituted of 12 subcarriersin the frequency domain. In the time domain, the uplink RB isconstituted of seven SC-FDMA symbols in a case that a normal cyclicprefix is added, while the uplink RB is constituted of six SC-FDMAsymbols in a case that a cyclic prefix that is longer than the normalcyclic prefix is added. Note that although an uplink subframe in asingle CC is described here, an uplink subfrarne is defined for each CC.For compensation of propagation delay and the like, the beginning of theradio frame in the uplink (uplink subframe) is adjusted to precede thebeginning of the radio frame in the downlink (downlink subframe), withrespect to the terminal device.

A synchronization signal is constituted by three kinds of primarysynchronization signals and secondary synchronization signalsconstituted by 31 kinds of codes that are interleaved in the frequencyregion. 504 patterns of cell identifiers (Physical Cell Identities;PCIs) for identifying base station devices, and frame timing for radiosynchronization are indicated by the combinations of the primarysynchronization signals and the secondary synchronization signals. Theterminal device identifies the physical cell ID of a receivedsynchronization signal by cell search.

The Physical Broadcast CHannel (PBCH) is transmitted for thenotification (configuration) of a control parameter (broadcastinformation i.e., system information) commonly used among the terminaldevices within the cell. The radio resource in which broadcastinformation is transmitted is announced on the physical downlink controlchannel to the terminal devices in the cell. Broadcast information notannounced on the physical broadcast information channel is transmitted,as a layer-3 message (system information) for announcing the broadcastinformation of the physical downlink shared channel, by the announcedradio resource.

Broadcast information to be notified includes, for example, a CellGlobal Identifier (CGI), which indicates a cell-specific identifier, aTracking Area Identifier (TAI) for managing standby areas in paging,random access configuration information (such as a transmission timingtimer), and shared radio resource configuration information, neighboringcell information and uplink access control information of the cell.

A downlink reference signal is classified into a plurality of typesaccording to its use. For example, cell-specific RSs (Cell-specificreference signals) are pilot signals transmitted with prescribed powerfrom each cell and are downlink reference signals periodically repeatedin the frequency domain and the time domain under a prescribed rule. Theterminal device receives the cell-specific RS and thus measures thereception quality of each cell. The terminal device also uses acell-specific RS as a reference signal for demodulation of a physicaldownlink control channel or a physical downlink shared channeltransmitted at the same time as a cell-specific RS. A sequencedistinguishable among the cells can be used for a sequence for acell-specific RS.

The downlink reference signal is also used for estimation of downlinkchannel fluctuation. A downlink reference signal used for estimation ofdownlink channel fluctuations is referred to as “Channel StateInformation Reference Signal (CSI-RS)”. A downlink reference signalindividually configured for the terminal device is referred to asUE-specific Reference signal (URS), a Demodulation Reference Signal(DMRS), or a Dedicated RS (DRS), and is referred to for a channelcompensation process for demodulating an enhanced physical downlinkcontrol channel or a physical downlink shared channel.

The Physical Downlink Control CHannel (PDCCH) occupying one or severalOFDM symbols (e.g., 1 to 4 OFDM symbols) from the start of each subframeis transmitted. The Enhanced Physical Downlink Control CHannel (EPDCCH)is a physical downlink control channel allocated to the OFDM symbols towhich the Physical Downlink Shared CHannel (PDSCH) is allocated. ThePDCCH or EPDCCH is used for notifying each terminal device of radioresource allocation information according to scheduling determined bythe, base station device and information indicating an adjustment amountfor an increase or decrease in transmit power. In the following, even ina case that the Physical Downlink Control CHannel (PDCCH) alone isdescribed, both physical channels that is, the PDCCH and the EPDCCH, areincluded unless otherwise noted.

The terminal device needs to monitor a physical downlink control channeladdressed to the terminal device itself, and receive the physicaldownlink control channel addressed to the terminal device itself, beforetransmitting and/or receiving downlink data or a layer-2 message orlayer-3 message, which is higher-layer control information (such as apaging or handover command), and thus acquire, from the physicaldownlink control channel, radio resource allocation information calleduplink grant in a case of transmission and downlink grant (downlinkassignment) in a case of reception. Note that it is also possible toconstitute the physical downlink control channel so that the physicaldownlink control channel is to be transmitted in the dedicated resourceblock domain allocated to each terminal device by the base stationdevice, instead of transmission through OFDM symbols described above.The uplink grant can be rephrased as a DCI format used for schedulingthe PUSCH. The downlink grant can be rephrased as a DCI format used forscheduling the PDSCH. The subframe for which the PDSCH is scheduled is asubframe for which the DCI format indicating reception of the PDSCH, hasbeen successfully decoded. The subframe for which the PUSCH is scheduledis indicated in association with the subframe for which the DCI formatindicating transmission of the PUSCH has been successfully decoded. Forexample, for FDD cells, the subframe for which the PUSCH is scheduled isthe fourth subframe following the subframe for which the DCI formatindicating transmission of the PUSCH has been successfully decoded. Inother words, each of the subframes for which the PUSCH and the PDSCH arescheduled is associated with the subframe for which the DCI formatindicating the transmission or reception of the channel has beensuccessfully decoded.

The Physical Uplink Control Channel (PUCCH) is used for anacknowledgment in response to reception of downlink data transmitted onthe physical downlink shared channel (HARQ-ACK; Hybrid Automatic RepeatreQuest-Acknowledgment or ACK/NACK; Acknowledgment/NegativeAcknowledgment), downlink channel (Channel State) Information (CSI), anduplink radio resource allocation request (radio resource request,Scheduling Request (SR)).

CSI includes a Channel Quality indicator (CQI) of the serving cellcorresponding to the CSI, a Precoding Matrix Indicator (PMI), aPrecoding Type Indicator (PTI), and a Rank Indicator (RI), which can beused respectively for specifying (representing) a preferable modulationscheme and coding rate, a preferable precoding matrix, a preferable PMItype, and a preferable rank. Indication may be used as a notation foreach indicator. Moreover, the CQI and the PMI are classified intowideband CQI and PMI assuming transmission using all the resource blocksin a single cell, and subband CQI and PMI assuming transmission usingsome contiguous resource blocks (subbands) in a single cell. Moreover,PMI may include a type of PMI, which represents a single preferableprecoding matrix using two types of PMIs, which are a first PMI and asecond PMI, in addition to a normal type of PMI, which represents asingle preferable precoding matrix using a single PMI.

For example, the terminal device 1 reports a CQI index that satisfies acondition that an error probability of one PDSCH transport occupying agroup of downlink physical resource blocks and determined by acombination of a modulation scheme and a transport block sizecorresponding to the CQI index, does not exceed a prescribed value (forexample, 0.1).

Note that each of the downlink physical resource blocks used tocalculate the CQI, the PMI, and/or the RI is referred to as a CSIreference resource.

The terminal device 1 reports the CSI to the base station device 2. TheCSI reporting includes periodic CSI reporting and aperiodic CSIreporting. In the periodic CSI reporting, the terminal device 1 reportsthe CSI at a timing configured by a higher layer. In the aperiodic CSIreporting, the terminal device 1 reports the CSI at a timing based onCSI request information included in the received uplink DCI format(uplink grant) or a random access response grant.

The terminal device 1 reports the CQI and/or the PMI and/or the RI. Notethat the terminal device 1 need not report the PMI and/or the RIdepending on a configuration made by a higher layer, The configurationmade by the higher layer includes, for example, a transmission mode, afeedback mode, a reporting type, and a parameter indicating whether toreport the PMI/RI.

Moreover, the terminal device 1 may be configured to perform one ormultiple CSI processes for one serving cell. The CSI process isconfigured in association with the CSI reporting. One CSI process isassociated with one CSI-RS resource and one CSI-IM resource.

The Physical Downlink Shared CHannel (PDSCH) is also used to notify theterminal device of a response to random access (Random Access Response(RAR)) and broadcast information (system information) that is notnotified by paging or on the physical broadcast information channel, inaddition to downlink data, as a layer-3 message. Radio resourceallocation information of the physical downlink shared channel isindicated by a physical downlink control channel. The physical downlinkshared channel is allocated to OFDM symbols other than the OFDM symbolsused to transmit a physical downlink control channel and is transmitted.In other words, the physical downlink shared channel and the physicaldownlink control channel are time division multiplexed in a singlesubframe.

The Physical Uplink Shared CHannel (PUSCH) mainly transmits uplink dataand uplink control information which may also include uplink controlinformation such as CSI and ACK/NACK. Moreover, the physical uplinkshared channel is also used such that the terminal device notifies thebase station device of uplink data as well as a layer-2 message and alayer-3 message, which are higher-layer control information. Radioresource allocation information of the physical uplink shared channel isprovided by a physical downlink control channel, as in a case ofdownlink.

An uplink reference signal (also referred to as “uplink pilot signal” or“uplink pilot channel”) includes a Demodulation Reference Signal (DMRS)to be used by the base station device to demodulate the physical uplinkcontrol CHannel PUCCH and/or physical uplink shared CHannel PUSCH, and aSounding Reference Signal (SRS) to he mainly used by the base stationdevice to estimate an uplink channel state. Moreover, sounding referencesignals are categorized into a periodic Sounding Reference Signal(Periodic SRS), which is transmitted periodically, or an AperiodicSounding Reference Signal (Aperiodic SRS), which is transmitted in acase that transmission is instructed by the base station device.

A Physical Random Access CHannel (PRACH) is a channel used for thenotification (configuration) of a preamble sequence and includes a guardtime. The preamble sequence is configured such that multiple sequencesare sued for notifying information to the base station device. Forexample, in a case that 64 sequences are available, 6-bit informationcan be provided to the base station device. A physical random accesschannel is used by the terminal device as a means for accessing the basestation device.

The terminal device uses the physical random access channel to requestan uplink radio resource in a case that no physical uplink controlchannel is configured for an SR or to request the base station devicefor a transmission timing adjustment information (also referred to asTiming Advance (TA) command) necessary for matching uplink transmissiontiming to a reception timing window of the base station device, forexample. Moreover, the base station device can request the terminaldevice to start a random access procedure, by using a physical downlinkcontrol channel.

The random access response is response information from the base stationdevice for random access by the terminal device. The random accessresponse is included in the PDSCH scheduled based on control informationfor the PDCCH having CRC scrambled with RA-RNTI, and the PDSCH istransmitted from the base station device. The random access responseincludes transmission timing adjustment information, the uplink grant(the uplink grant included in the random access response is alsoreferred to as a random access response grant), and Temporary C-RNTIinformation, which is a temporary identifier of the terminal device.

A layer-3 message is a message exchanged between the Radio ResourceControl (RRC) layers of the terminal device and the base station deviceand handled in a protocol for a Control-plane (CP (C-Plane)), and may beused synonymly with RRC signaling or RRC message. A protocol handlinguser data (uplink data. and downlink data) is referred to as “User-plane(UP (U-Plane))” in contrast to “control plane”. Here, a transport blockthat is transmission data in the physical layer includes C-Planemessages and U-Plane data in higher layers. Detailed descriptions ofother physical channels are omitted.

A communicable range (communication area) at each frequency controlledby a base station device is regarded as a cell. Here, the communicationarea covered by the base station device may be different in size andshape for each frequency. Moreover, the covered area may be differentfor each frequency. A radio network, in which cells having differenttypes of base station devices or different cell radii are located in amixed manner in the area with the same frequency and/or differentfrequencies to form a single communication system, is referred to as aheterogeneous network.

The terminal device operates by regarding the inside of a cell as acommunication area. In a case that the terminal device moves from a cellto a different cell, the terminal device moves to an appropriatedifferent cell through a cell reselection procedure at the time ofhaving no radio connection (during no communication) and through ahandover procedure at the time of having radio connection (duringcommunication). A suitable cell in general indicates a cell that isdetermined that access from the terminal device is not prohibited basedon information specified by the base station device, and that has adownlink reception quality satisfying a predefined condition.

Moreover, the terminal device and the base station device may employ atechnique for aggregating the frequencies (component carriers orfrequency band) of a plurality of different frequency bands throughCarrier Aggregation and treating the resultant as a single frequency(frequency band). A component carrier is categorized as an uplinkcomponent carrier corresponding to the uplink and a downlink componentcarrier corresponding to the downlink. In this specification,“frequency” and “frequency band” may be used synonymously.

For example, in a case that each of five component carriers havingfrequency bandwidths of 20 MHz are aggregated through CarrierAggregation, a terminal device capable of performing Carrier Aggregationperforms transmission and/or reception by assuming that the aggregatedcarriers have a frequency bandwidth of 100 MHz. Note that componentcarriers to be aggregated may have contiguous frequencies or frequenciessome or all of which are discontiguous. For example, assuming thatavailable frequency bands include an 800 MHz band, a 2 GHz band, and a3.5 GHz band, a component carrier may be transmitted in the 800 MHzband, another component carrier may be transmitted in the 2 GHz band,and yet another component carrier may be transmitted in the 3.5 GHzband.

It is also possible to aggregate multiple contiguous or discontiguouscomponent carriers of the same frequency bands. The frequency bandwidthof each component carrier may be narrower 5 MHz or 10 MHz) than thereceivable frequency bandwidth (e.g., 20 MHz) of the terminal device,and the frequency bandwidth of component carriers to be aggregated maybe different from each other. Each frequency bandwidth may be equal toany of the frequency bandwidth of known cells in consideration ofbackward compatibility, but may be a frequency bandwidth different fromany of the frequency bands of the known cells.

Moreover, component carriers (carrier types) without backwardcompatibility may be aggregated. Note that the number of uplinkcomponent carriers to be allocated to (configured for or added for) theterminal device by the base station device may he the same as or may befewer than the number of downlink component carriers.

A cell constituted of an uplink component carrier in which an uplinkcontrol channel is configured for a radio resource request and adownlink component carrier having a cell-specific connection with theuplink component carrier is referred to as “Primary cell (PCell).” Acell constituted of component carriers other than those of the primarycell is referred to as “Secondary cell (SCell).” The terminal devicereceives a paging message, detects update of broadcast information,carries out an initial access procedure, configures securityinformation, and the like in a primary cell, and need not perform theseoperations in secondary cells.

Although a primary cell is not a target of activation and deactivationcontrols (in other words, considered as being activated at any time), asecondary cell has activated and deactivated states, the change of whichis explicitly specified by the base station device or is made based on atimer configured for the terminal device for each component carrier. Theprimary cell and secondary cell are collectively referred to as “servingcell”.

Carrier Aggregation achieves communication using multiple componentcarriers (frequency bands) using multiple cells, and is also referred toas cell aggregation. The terminal device may have radio connection withthe base station device via a relay station device (or repeater) foreach frequency. In other words, the base station device of the presentembodiment may be replaced with a relay station device.

The base station device manages a cell, which corresponds to an areawhere terminal devices can communicate with the base station device, foreach frequency. A single base station device may manage multiple cells.Cells are classified into multiple types of cells depending on the sizeof the area (cell size) that allows for communication with terminaldevices. For example, cells are classified into macro cells and smallcells. Moreover, small cells are classified into femto cells, picacells, and nano cells depending on the size of the area. In a case thata terminal device can communicate with a certain base station device,the cell configured so as to be used for the communication with theterminal device is referred to as “Serving cell” while the other cellsnot used for the communication are referred to as “Neighboring cell”,among the cells of the base station device.

In other words, in Carrier Aggregation, a plurality of serving cellsthus configured include one primary cell and one or a plurality ofsecondary cells.

A primary cell is a serving cell in which an initial connectionestablishment procedure has been carried out, a serving cell in which aconnection re-establishment procedure has been started, or a cellindicated as a primary cell during a handover procedure. The primarycell operates at a primary frequency. At the point of time when aconnection is (re)established, or later, a secondary cell may beconfigured. Each secondary cell operates at a secondary frequency. Theconnection may be referred to as an RRC connection. For the terminaldevice supporting CA, a single primary cell and one or more secondarycells are aggregated.

In the present embodiment, Licensed Assisted Access (LAA) is used.According to LAA, an allocated frequency is configured to (used for) theprimary cell, and a non-allocated frequency is configured to at leastone of secondary cells. The secondary cell(s) to which the non-allocatedfrequency is configured is assisted by the primary cell or the secondarycell(s) to which the allocated frequency is configured. For example, theprimary cell(s) or the secondary cell to which the allocated frequencyis configured performs the configuration and/or announces controlinformation by the RRC signaling, MAC signaling and/or PDCCH signalingto the secondary cell(s) to which the non-allocated frequency isconfigured. In the present embodiment, a cell assisted by the primarycell or the secondary cell(s) is also referred to as “LAA cell”. The LAAcell can be aggregated (assisted) with the primary cell and/or thesecondary cell(s) by carrier aggregation. The primary cell or thesecondary cell(s) which assists the LAA cell is also referred to as“assist cell”.

The LAA cell may be aggregated (assisted) by the primary cell and/or thesecondary cell(s) by dual connectivity.

A basic configuration (architecture) of dual connectivity will bedescribed below. For example, the description will be given in a casethat a terminal device 1 connects to multiple base stations 2 (forexample, a base station device 2-1 and a base station device 2-2) at thesame time. The base station device 2-1 is a base station deviceconstituting a macro cell, and the base station device 2-2 is a basestation device constituting a small cell. The terminal device 1connecting to the base station devices 2 at the same time by using theplurality of cells belonging to the plurality of base station devices 2as described above is referred to as “dual connectivity”. The cellsbelonging to the respective base station devices 2 may be operated atthe same frequency or different frequencies.

Note that Carrier Aggregation is different from dual connectivity inthat a single one of the base station devices 2 manages a plurality ofcells and the frequencies of the respective cells are different fromeach other. In other words, Carrier Aggregation is a technique forconnecting the single terminal device 1 and a single one of the basestation device 2 via a plurality of cells having different frequencies,while dual connectivity is a technique for connecting the singleterminal device 1 and the plurality of base station devices 2 via aplurality of cells having the same frequency or different frequencies.

The terminal device 1 and base station devices 2 can apply a techniqueused for Carrier Aggregation, to dual connectivity. For example, theterminal device 1 and base station devices 2 may apply a technique ofallocation of a primary cell and secondary cells oractivation/deactivation, to cells connected through dual connectivity.

In dual connectivity, the base station device 2-1 or base station device2-2 is connected to MME and SGW via a backbone network. The MME is ahost control station device corresponding to a Mobility ManagementEntity (MME) and has the functions of managing mobility and performingauthentication control (security control) for the terminal device 1, andconfiguring routes for user data to the base station devices 2. The SGWis a host control station device corresponding to a Serving Gateway(S-GW) and has the functions of transmitting user data according to theroute for user data to the terminal device 1 configured by the MME.

Moreover, in dual connectivity, the connection route between the basestation device 2-1 or base station device 2-2 and the SGW is referred toas an “SGW interface”. Moreover, the connection route between the basestation device 2-1 or base station device 2-2 and the MME is referred toas “MME interface”. Moreover, the connection route between the basestation device 2-1 and base station device 2-2 is referred to as “basestation interface”. The SGW interface is also referred to as an S1-Uinterface in EUTRA. Moreover, the MME interface is also referred to as“S1-MME interface” in EUTRA. Moreover, the base station interface isalso referred to as “X2 interface” in EUTRA.

An example of an architecture for enabling dual connectivity will bedescribed. In dual connectivity, the base station device 2-1 and the MMEare connected via the MME interface. Moreover, the base station device2-1 and the SGW are connected via the SGW interface. Moreover, the basestation device 2-1 provides, to the base station device 2-2, thecommunication route to the MME and/or SGW via the base stationinterface. In other words, the base station device 2-2 is connected tothe MME and/or the SGW via the base station device 2-1.

Moreover, another example of another architecture for enabling dualconnectivity will be described. In dual connectivity, the base stationdevice 2-1 and the MME are connected via the MME interface. Moreover,the base station device 2-1 and the SOW are connected via the SGWinterface. The base station device 2-1 provides, to the base stationdevice 2-2, the communication route to the MME via the base stationinterface. In other words, the base station device 2-2 is connected tothe MME via the base station device 2-1. Moreover, the base stationdevice 2-2 is connected to the SOW via the SGW interface.

Note that a constitution in which the base station device 2-2 and theMME are directly connected via the MME interface may be employed.

On the basis of description from a different point of view, dualconnectivity is an operation whereby a prescribed terminal deviceconsumes radio resources provided from at least two different networkpoints (master base station device (MeNB or Master eNB) and secondarybase station device (SeNB or Secondary eNB)). In other words, in dualconnectivity a terminal device is configured to establish an RRCconnection to at least two network points. In dual connectivity, theterminal device may be connected via a non-ideal backhaul in RRCconnected (RRC_CONNECTED) state.

In dual connectivity, a base station device that is connected to atleast the S1-MME and that acts as the mobility anchor of the corenetwork is referred to as “master base station device”. Moreover, a basestation device that is not the master base station device and thatprovides supplemental radio resources to the terminal device is referredto as “secondary base station device.” A group of serving cells that isassociated with the master base station device may be referred to as“Master Cell Group” (MCG), and a group of serving cells that isassociated with the secondary base station device may be referred to as“Secondary Cell Group” (SCG). Note that the cell groups may he servingcell groups.

In dual connectivity, the primary cell belongs to the MCG Moreover, inthe SCG, the secondary cell corresponding to the primary cell isreferred to as “Primary Secondary Cell” (pSCell). Note that the pSCellmay be referred to as “special cell” or “Special Secondary Cell”(Special SCell). Some of the functions (for example, functions fortransmitting and/or receiving a PUCCH) of the PCell (the base stationdevice constituting the PCell) may be supported by the Special SCell(the base station device constituting the Special SCell). Additionally,some of the functions of the PCell may he supported in the pSCell. Forexample, the function for transmitting a PDCCH may be supported by thepSCell. Additionally, the function for performing a PDCCH transmissionmay be supported in the pSCell by using a search space different from aCommon Search Space (CSS) or a UE-specific Search Space (USS). Forexample, the search space different from a USS is a search spacedetermined based on a value defined in the specification, a search spacedetermined based on an RNTI different from a C-RNTI, a search spacedetermined based on a value configured by a higher layer that isdifferent from the RNTI, or the like. Moreover, the pSCell mayconstantly be in a starting state. Moreover, the pSCell is a cellcapable of receiving the PUCCH.

In dual connectivity, the Data Radio Bearer (DRB) may be individuallyallocated to the MeNB and the SeNB. On the other hand, the SignallingRadio Bearer (SRB) may be allocated only to the MeNB. In dualconnectivity, a duplex mode may he configured individually for the MCGand the SCG or the PCell and the pSCell. In dual connectivity, the MCGand the SCG or the PCell and the pSCell need not necessarily besynchronized with each other. In dual connectivity; a plurality ofparameters for timing adjustment (TAG or Timing Advance Group) may beconfigured for each of the MCG and the SCG. In other words, the terminaldevice is capable of performing uplink transmission at a plurality ofdifferent timings in each CG.

In dual connectivity, the terminal device is allowed to transmit UCIcorresponding to the cells in the MCG only to the MeNB (the PCell) andto transmit UCI corresponding to the cells in the SCG to SeNB (thepSCell) only. For example, the UCI is an SR, HARQ-ACK, and/or CSI.Additionally, in each UCI transmission, a transmission method using thePUCCH and/or the PUSCH is applied to each cell group.

All signals can be transmitted and/or received in the primary cell, butsome signals may not be transmitted and/or received in the secondarycell. For example, a Physical Uplink Control CHannel (PUCCH) istransmitted only in the primary cell. Additionally, unless a pluralityof Timing Advance Groups (TAGs) are configured between the cells, aPhysical Random Access CHannel (PRACH) is transmitted only in theprimary cell. Additionally, a Physical Broadcast CHannel (PBCH) istransmitted only in the primary cell. Additionally, a Master InformationBlock (MIB) is transmitted only in the primary cell. Signals that can betransmitted and/or received in the primary cell are transmitted and/orreceived in the primary secondary cell. For example, the PUCCH may betransmitted in the primary secondary cell. Additionally, the PRACH maybe transmitted in the primary secondary cell, regardless of whether aplurality of TAGs are configured. Additionally, the PBCH and the MIB maybe transmitted in the primary secondary cell.

In the primary cell, Radio Link Failure (RLF) is detected. In thesecondary cell, even if conditions for the detection of RLF are inplace, the detection of the RLF is not recognized. However, in theprimary secondary cell, the RLF is detected if the conditions are inplace. In a case that an RLF is detected in the primary secondary cell,the higher layer of the primary secondary cell announces, to the higherlayer of the primary cell, that the RLF has been detected.Semi-Persistent Scheduling (SPS) or Discontinuous Reception (DRX) may beused in the primary cell. The same DRX as in the primary cell may beused in the secondary cell. Fundamentally, in the secondary cell, theMAC configuration information/parameters are shared with the primarycell/primary secondary cell of the same call group. Some of theparameters (for example, STAG-Id) may be configured for each secondarycell. Some of the timers or counters may be applied only to the primarycell and/or the primary secondary cell. A timer or counter to be appliedmay be configured only to the secondary cell.

In an example where dual connectivity is applied to the LAA cell, theMCG (base station device 2-1) is a base station device which constitutesthe primary cell. The SCG (base station device 2-2) is a base stationdevice which constitutes the LAA cell. In other words, the LAA cell isconfigured as pSCell of the SCG.

In another example where dual connectivity is applied to the LAA cell,the MCG is the base station device which constitutes the primary cell,and the SCG is the base station device which constitutes the pSCell andthe LAA cell. In other words, the LAA cell is assisted by the pSCell inthe SCG. Note that in a case that the secondary cell is furtherconfigured to the SCG, the LAA cell may be assisted by the secondarycell.

In still another example where dual connectivity is applied to the LAAcell, the MCG is the base station device which constitutes the primarycell and the LAA cell, and the SCG is the base station device whichconstitutes the pSCell. In other words, the LAA cell is assisted by theprimary cell in the MCG. Note that in a case that the secondary cell isfurther configured to the MCG, the LAA cell may be assisted by thesecondary cell.

FIG. 3 is a schematic diagram illustrating an example of a blockconfiguration of a base station device 2 according to the presentembodiment. The base station device 2 includes a higher layer(higher-layer control information notification unit, higher layerprocessing unit) 301, a control unit (base station control unit) 302, acodeword generation unit 303, a downlink subframe generation unit 304,an OFDM signal transmission unit (downlink transmission unit) 306, atransmit antenna (base station transmit antenna) 307, a receive antenna(base station receive antenna) 308, an SC-FDMA signal reception unit(CSI reception unit) 309, and an uplink subframe processing unit 310.The downlink subframe generation unit 304 includes a downlink referencesignal generation unit 305. Moreover, the uplink subframe processingunit 310 includes an uplink control information extraction unit (CSIacquisition unit) 311.

FIG. 4 is a schematic diagram illustrating an example of a blockconfiguration of a terminal device 1 according to the presentembodiment. The terminal device 1 includes a receive antenna (terminalreceive antenna) 401, an OFDM signal reception unit (downlink receptionunit) 402, a downlink subframe processing unit 403, a transport blockextraction unit (data extraction unit) 405, a control unit (terminalcontrol unit) 406, a higher layer (higher-layer control informationacquisition unit, higher layer processing unit) 407, a channel statemeasurement unit (CSI generation unit) 408, an uplink subframegeneration unit 409, an SC-FDMA signal transmission unit (UCItransmission unit) 411, and a transmit antenna (terminal transmitantenna) 412. The downlink subframe processing unit 403 includes adownlink reference signal extraction unit 404. Moreover, the uplinksubframe generation unit 409 includes an uplink control informationgeneration unit (UCI generation unit) 410.

First, a flow of downlink data transmission and/or reception will bedescribed with reference to FIG. 3 and FIG. 4. In the base stationdevice 2, the control unit 302 holds a Modulation and Coding Scheme(MCS) indicating a modulation scheme, a coding rate, and the like in thedownlink, a downlink resource allocation indicating RBs to be used fordata transmission, and information to be used for HARQ control (aredundancy version, an HARQ process number, and a new data indicator)and controls the codeword generation unit 303 and the downlink subframegeneration unit 304, based on these elements. Downlink data (alsoreferred to as a downlink transport block) transmitted from the higherlayer 301 is processed through error correction coding, rate matching,and the like in the codeword generation unit 303 under the control ofthe control unit 302 and then, a codeword is generated. Two codewords atmaximum are transmitted at the same time in a single subframe of asingle cell. The control unit 302 instructs the downlink subframegeneration unit 304 to generate a downlink subframe. First, a codewordgenerated in the codeword generation unit 303 is converted into amodulation symbol sequence through a modulation process, such as PhaseShift Keying (PSK) modulation or Quadrature Amplitude Modulation (QAM).Moreover, a modulation symbol sequence is mapped onto REs of some RBs,and a downlink subfrarne for each antenna port, is generated through aprecoding process. In this operation, the transmission data sequencetransmitted from the higher layer 301 includes higher-layer controlinformation, which is control information about the higher layer (e.g.,dedicated (individual) Radio Resource Control (RRC) signaling).Furthermore, the downlink reference signal generation unit 305 generatesa downlink reference signal. The downlink subframe generation unit 304maps the downlink reference signal to the REs in the downlink subframesin accordance with an instruction from the control unit 302. The OFDMsignal transmission unit 306 modulates the downlink subframe generatedby the downlink subframe generation unit 304 to an OFDM signal, and thentransmits the OFDM signal through the transmit antenna 307. Although aconfiguration of including one OFDM signal transmission unit 306 and onetransmit antenna 307 is illustrated as an example here, a configurationof including multiple OFDM signal transmission units 306 and multipletransmit antennas 307 may be employed for transmitting downlinksubframes through multiple antenna ports. Furthermore, the downlinksubfrarne generation unit 304 may also have a capability of generatingphysical-layer downlink control channels, such as a PDCCH and an EPDCCHto map the channels to REs in downlink subframes. Multiple base stationdevices (base station device 2-1 and base station device 2-2) transmitseparate downlink subframes. Note that the base station device 2 thatoperates in the LAA cell is configured to include a CCA check unit 312configured to determine whether the channel is idle or busy. The CCAcheck unit 312 is implemented with a method for determination usingpower received through the receive antenna 308, a method for adetermination depending on whether a specific signal from the uplinksubframe processing unit 310 has been detected, and the like. Adetermination result from the CCA check unit 312 is transmitted to thecontrol unit 302 and used to control the transmission.

In the terminal device 1, an OFDM signal is received by the OFDM signalreception unit 402 through the receive antenna 401, and an OFDMdemodulation process is performed on the signal. The downlink subframeprocessing unit 403 first detects physical-layer downlink controlchannels, such as a PDCCH and an EPDCCH. More specifically, the downlinksubframe processing unit 403 decodes the signal by assuming that a PDCCHand an EPDCCH have been transmitted in the regions to which the PDCCHand the EPDCCH can be allocated, and checks Cyclic Redundancy Check(CRC) bits added in advance (blind decoding). In other words, thedownlink subframe processing unit 403 monitors a PDCCH and an EPDCCH. Ina case that the CRC bits match an ID (a single terminal-specificidentifier assigned to a single terminal, such as a Cell-Radio NetworkTemporary Identifier (C-RNTI) or a Semi Persistent Scheduling-C-RNTI(SPS-C-RNTI), or a Temporary C-RNTI) assigned by the base station devicebeforehand, the downlink subframe processing unit 403 recognizes that aPDCCH or an EPDCCH has been detected and extracts a PDSCH by usingcontrol information included in the detected PDCCH or EPDCCH. Thecontrol unit 406 holds an MCS indicating a modulation scheme, a codingrate, and the like in the downlink based on the control information, adownlink resource allocation indicating RBs to be used for downlink datatransmission, and information to be used for HARQ control, and controlsthe downlink subframe processing unit 403, the transport blockextraction unit 405, and the like, in accordance with these elements.More specifically, the control unit 406 performs control so as to carryout an RE mapping process in the downlink subfrarne generation unit 304,an RE demapping process and demodulation process corresponding to themodulation process, and the like. The PDSCH extracted from the receiveddownlink subframe is transmitted to the transport block extraction unit405. Furthermore, the downlink reference signal extraction unit 404 inthe downlink subframe processing unit 403 extracts the downlinkreference signal from the downlink subframe. The transport blockextraction unit 405 extracts a transport block that has been subjectedto a rate matching process, a rate matching process corresponding toerror correction coding, error correction decoding, and the like in thecodeword generation unit 303, and transmits the extracted transportblock to the higher layer 407. The transport block includes higher-layercontrol information, and the higher layer 407 notifies the control unit406 of a necessary physical-layer parameter, based on the higher-layercontrol information. The plurality of base station devices 2 (basestation device 2-1 and base station device 2-2) transmit separatedownlink subframes, and the terminal device 1 receives the downlinksubframes. Hence, the above-described processes may be carried out forthe downlink subframe of each of the plurality of base station devices2. In this situation, the terminal device 1 may recognize or may notnecessarily recognize that multiple downlink subframes have beentransmitted from the multiple base station devices 2. In a case that theterminal device 1 does not recognize the subframes, the terminal device1 may simply recognize that multiple downlinks subframes have beentransmitted in multiple cells. Moreover, the transport block extractionunit 405 determines whether the transport block has been detectedcorrectly, and transmits a determination result to the control unit 406.Note that the terminal device 1 that operates in the LAA cell isconfigured to include a CCA check unit 413 configured to determinewhether the channel is idle or busy. The CCA check unit 413 isimplemented with a method for determination using power received throughthe receive antenna 401, a method for determination depending on whethera specific signal from the downlink subframe processing unit 403 hasbeen detected, and the like. A determination result from the CCA checkunit 413 is transmitted to the control unit 406 and used to control thetransmission.

Next, a flow of uplink signal transmission and/or reception will bedescribed. In the terminal device 1, the control unit 406 instructs adownlink reference signal extracted by the downlink reference signalextraction unit 404 to be transmitted to the channel state measurementunit 408, and then instructs the channel state measurement unit 408 tomeasure the channel state and/or interference, and further to calculateCSI, based on the measured channel state and/or interference. Thecontrol unit 406 instructs the uplink control information generationunit 410 to generate an HARQ-ACK (DTX (not transmitted yet), ACK(detection success), or NACK (detection failure)) and to map theHARQ-ACK to a downlink subframe, based on a determination result ofwhether the transport block is correctly detected. The terminal device 1performs these processes on the downlink subframe of each of multiplecells. In the uplink control information generation unit 410, a PUCCHincluding the calculated CSI and/or HARQ-ACK is generated. In the uplinksubframe generation unit 409, the PUSCH including the uplink datatransmitted from the higher layer 407 and the PUCCH generated by theuplink control information generation unit 410 are mapped to RBs in anuplink subframe, and an uplink subframe is generated. The uplinksubframe is subjected to the SC-FDMA modulation in the SC-FDMA signaltransmission unit 411 to generate an SC-FDMA signal, and the SC-FDMAsignal transmission unit 411 transmits the SC-FDMA signal via thetransmit antenna 412.

Here, the terminal device 1 performs (derives) channel measurement forcalculating the value of the CQI, based on the CRS or the CSI-RS(non-zero power CSI-RS). Whether the terminal device I derives thechannel measurement, based on the CRS or the CSI-RS, is determinedaccording to higher layer signaling. Specifically; in a transmissionmode configured with the CSI-RS, the terminal device 1 derives thechannel measurement for calculating the CQI, based only on the CSI-RS.Specifically, in a transmission mode not configured with the CSI-RS, theterminal device 1 derives the channel measurement for calculating theCQI, based on the CRS. The RS used for the channel measurement forcalculating the CSI is also referred to as a first RS.

Here, the terminal device 1 performs (derives) interference measurementfor calculating the CQI, based on CSI-IM or a second RS, in a case thatthis is configured by the higher layer. Specifically, in a transmissionmode configured with the CSI-IM, the terminal device 1 derives theinterference measurement for calculating the CQI, based on the CSI-IM.Specifically, in the transmission mode configured with the CSI-IM, theterminal device 1 derives the interference measurement for calculatingthe value of the CQI corresponding to the CSI process, based only on theCSI-IM resource associated with the CSI process. The RS or IM used forthe channel measurement for calculating the CSI is also referred to as asecond RS.

Note that the terminal device 1 may perform (may derive) theinterference measurement for calculating the CQI, based on the CRS. Forexample, the terminal device 1 may derive the interference measurementfor calculating the CQI, based on the CRS, in a case that the CSI-IM isnot configured.

Note that the channel and/or interference used to calculate the CQI maysimilarly he used as a channel and/or interference for calculating thePMI or RI.

Details of the LAA cell will be described below.

The frequency used by the LAA cell is shared with other communicationsystems and/or other LTE operators. To share the frequency, the LAA cellneeds fairness with the other communication systems and/or the other LTEoperators. For example, a communication method used by the LAA cellneeds a fair frequency sharing technique (method). In other words, theLAA cell is a cell which performs a communication method (communicationprocedure) to which the fair frequency sharing technique is applicable(used).

An example of the fair frequency sharing technique is Listen-Before-Talk(LBT). Before a certain base station or a certain terminal transmits asignal by using a frequency (a component carrier, a carrier, a cell, achannel, or a medium), LBT measures (detects) interference power (aninterference signal, receive power, a receive signal, noise power and anoise signal) or the like of the frequency, to identify (detect, assumeor determine) whether the frequency is in an idle state (a free state, anon-congested state, Absence or Clear) or a busy state (an occupiedstate, a congested state, Presence or Occupied). In a case that thefrequency being in the idle state is identified based on LBT, the LAAcell can transmit a signal at a prescribed timing of the frequency. In acase that the frequency is identified as the busy state, the LAA celldoes not transmit a signal at the prescribed timing of the frequency.LBT controls and prevents an interference with signals to be transmittedby other communication systems and/or other base stations includingother LTE operators and/or terminals. Note that LBT performed by thebase station device before a downlink transmission is referred to asdownlink LBT and that LBT performed by the terminal device before anuplink transmission is referred to as uplink LBT. Furthermore, LBTperformed by the terminal device for sidelink transmissions may bereferred to as sidelink LBT.

An LBT procedure is defined as a mechanism to which Clear ChannelAssessment (CCA) check is applied before a certain base station orterminal uses the frequency (channel). The CCA performs power detectionor signal detection for determining presence of absence of anothersignal in the channel to identify whether the frequency is in the idlestate or the busy state. Note that in the present embodiment, adefinition of CCA may be equivalent to a definition of LBT. Note that,in the present embodiment, CCA is also referred to as carrier sense.

CCA can use various methods as a method for determining the presence orabsence of another signal. For example, CCA makes the determinationbased on whether the interference power at a certain frequency exceeds acertain threshold. Moreover, for example, CCA makes the determinationbased on whether the receive power of a prescribed signal or channel ata certain frequency exceeds a certain threshold. The threshold may bedefined in advance. The threshold may be configured by a base station oranother terminal. The threshold may be determined (configured) based onat least another value (parameter) such as transmit power (maximumtransmit power). Moreover, for example, CCA makes the determination,based on whether a prescribed channel at a certain frequency has beendecoded.

The LBT procedure includes Initial CCA (ICCA, single sensing, LBTcategory 2, Frame-Based Equipment (FBE)) allowing a signal to betransmitted after a CCA check is performed once, and Extended CCA (ECCA,multiple sensing, LBT category 3/4, Load-Based Equipment (LBE)) allowinga signal to be transmitted after the CCA check is performed a prescribednumber of times. A period in which the CCA check is performed by ICCA isreferred to as an ICCA period or an ICCA slot length, and lasts, forexample, 34 microseconds. Furthermore, a period in which the CCA checkis performed by ECCA is referred to as an ECCA period or an ECCA slotlength, and lasts, for example, 9 microseconds. Note that the prescribednumber of times is also referred to as a backoff counter (counter,random number counter, ECCA counter). Furthermore, a period in which theCCA check is performed after the frequency changes from the busy stateto the idle state is referred to as a defer period or an ECCA deferperiod, and lasts, for example, 34 microseconds.

FIG. 6 illustrates an example of an LBT (LBT category 4, LBE) procedurefor a downlink transmission. In a case that the need arises to transmit,to the terminal device, certain information (data, a buffer, load,traffic) in the downlink while the channel is in the idle state (S601)of waiting for a downlink transmission, the base station devicedetermines whether the transmission is needed (S602) and proceeds toinitial CCA (S603). In the initial CCA, the base station device performsthe CCA check during an initial CCA period to sense whether the channelis idle or busy (S6031). In a case of determining that the channel isidle as a result of the initial CCA (S603), the base station deviceacquires the right to access the channel and proceeds to a transmissionoperation. Then, the base station device determines whether to actuallyperform a downlink transmission at that timing (S604), and in a case ofdetermining to perform the downlink transmission, the base stationdevice performs the downlink transmission (S605). After performing thedownlink transmission, the base station device determines whether anyinformation that needs another downlink transmission is still present(remains) (S606). In a case that no information that needs anotherdownlink transmission has been generated yet (remains), the channelreturns to the idle state (S601). On the other hand, in a case that theinitial CCA (S603) results in the determination that the channel is busyor that the determination of whether any information that needs anotherdownlink transmission is still present (remains) (S606) results in thedetermination that information that needs another downlink transmissionis still present (remains), the base station device proceeds to theextended CCA (S607). In the extended CCA, first, the base station devicerandomly generates a counter value N within the range from 0 to q-1(S6071). The base station device then senses whether the channel is idleor busy in the ECCA defer occasion (S6072). In a case of determiningthat the channel is busy in the ECCA defer occasion, the base stationdevice senses again whether the channel is idle or busy in the ECCAdefer occasion (6072). On the other hand, in a case of determining thatthe channel is idle in the ECCA defer occasion, then the base stationdevice senses the channel (medium) during one ECCA slot duration (S6073)to determine whether the channel is idle or busy (6074). The basestation device decrements the counter value N by one (S6075) in a caseof determining that the channel is idle, and returns to the process ofsensing the channel in the ECCA defer occasion (S6072) again in a caseof determining that the channel is busy. The base station device thendetermines whether the counter value is 0 (S6076), and in a case thatthe counter value is 0, proceeds to a transmission process (S604, S605).On the other hand, in a case that the counter value is not 0, the basestation device senses the channel (medium) during one ECCA slot durationagain (S6073). Note that, in a case that the counter value N isgenerated, a value in a collision window q is updated to a. valuebetween X and Y according to a channel state (S6077).

The value in the collision window q is determined, for example, based onthe HARQ-ACK response in the PDSCH transmitted by the base stationdevice, a power value obtained by sensing of the channel by the basestation device, reporting of RSRP, RSRQ, and/or RSSI, or the like. Thevalue in the collision window q is, by way of example, exponentiallyincreased. Furthermore, the minimum value X and the maximum value Y usedto determine the value in the collision window q are parametersconfigured by the higher layer.

In the LBT procedure in FIG. 6, the extended CCA may not be performed.Specifically, in a case of determining that the channel is busy as aresult of the initial CCA (S603), the base station device may return tothe idle state (S601) instead of proceeding to the extended CCA process(S607). Furthermore, even in a case that, after a downlink transmission,information that needs another downlink transmission is still present(S606), the base station device may return to the idle state (S601)instead of proceeding to the extended CCA process (S607). LBT involvingsuch a process is also referred to as LBT category 2. LBT involving sucha process may be applied as LBT for a DS transmission, a PDSCHtransmission with a time length of 1 ms or shorter, or a transmissiononly of the PDCCH, for example.

Note that CCA in the LAA cell does not need to be recognized by theterminal connected with (configured to) the LAA cell.

In a case that the terminal device 1 can detect a transmission after CCAis completed in the LAA cell, the terminal device 1 may assume thatconsecutive transmissions are performed for several subframes afterdetection of the first transmission. Several subframes for consecutivetransmissions are also referred to as a transmission burst. Inparticular, several subframes for consecutive PDSCH transmissions arereferred to as a PDSCH transmission burst. The PDSCH transmission burstmay include a channel other than the PDSCH and/or a signal. For example,the PDSCH transmission burst may include the PDSCH and the DS and betransmitted. Moreover, in particular, several subframes for which onlythe DS is transmitted are referred to as a DS transmission burst. Thenumber of subframes for consecutive transmissions through thetransmission burst may be configured for the terminal device 1 by usingan RRC message. In the present embodiment, the transmission burst of thedownlink signal or channel is also referred to as a downlinktransmission, and the transmission burst of the uplink signal or channelis also referred to as an uplink transmission.

In a case of detecting a reservation signal included in the beginning ofthe transmission burst, the terminal device can sense the transmissionburst. The terminal device regards several subframes following thesubframe in which the reservation signal has been detected, as atransmission burst. In a case that a first synchronization signal, asecond synchronization signal, or a third synchronization signaldescribed below is detected, instead of the reservation signal, theterminal device can determine the following several subframes as atransmission burst.

Furthermore, the terminal device can sense a transmission burst in acase of decoding information included in the DCI and relating to asubframe indicating a transmission burst. The DCI is included in thePDCCH or EPDCCH allocated in the CSS for notification. Alternatively,the DCI may be included in the PDCCH or EPDCCH allocated in the USS fornotification.

The LAA cell may he defined as a cell different from a. secondary cellwhich uses the allocated frequency. For example, the LAA cell isconfigured differently from the configuration of the secondary cellwhich uses the allocated frequency. Part of parameters configured to theLAA cell is not configured to the secondary cell which uses theallocated frequency. Part of the parameters configured to the secondarycell which uses the allocated frequency is not configured to the LAAcell. In the present embodiment, the LAA cell is described as a celldifferent from the primary cell and the secondary cell(s), but the LAAcell may be defined as one of the secondary cells. Secondary cells ofthe related art are also referred to as “first secondary cells”, and theLAA cell is also referred to as “second secondary cell”. A primary celland secondary cell(s) of the related art are also referred to as “firstserving cells”, and the LAA cell is also referred to as “second servingcell”.

The LAA cell may be different from a frame structure type of the relatedart. For example, a first frame structure type (FDD, frame structuretype 1) or a second frame structure type (TDD, frame structure type 2)are used for (configured to) the serving cells in the related art, and athird frame structure type (frame structure type 3) is used for(configured to) the LAA cell. Note that either an LAA cell of the firstframe structure type or an LAA cell of the second frame structure typemay be used (may be configured).

Moreover, the third frame structure type may he preferably a framestructure type corresponding to a TDD cell that can performtransmissions at the same frequency both in the uplink and in thedownlink while having characteristics of an FDD cell. For example, thethird frame structure type may have uplink subframes, downlinksubframes, and special subframes but may be similar to the FDD cell interms of an interval from reception of the uplink grant until atransmission of the PUSCH scheduled in the uplink grant or an intervalfrom reception of the PDSCH to HARQ feedback to the PDSCH.

Furthermore, the third frame structure type may be preferably a framestructure type independent of a TDD UpLink/DownLink (TDD UL/DL)configuration in the related art. For example, the uplink subframes, thedownlink subframes, and the special subframes may be aperiodicallyconfigured for the radio frame, For example, the uplink subframes, thedownlink subframes, and the special subframes may be determined based onthe PDCCH or the EPDCCH.

Here, the non-allocated frequency is a frequency different from theallocated frequency that is allocated as a dedicated frequency to aprescribed operator. For example, the non-allocated frequency is afrequency used by a wireless LAN. For example, the non-allocatedfrequency is a frequency which is not configured to the LTE in therelated art, and the allocated frequency is a frequency which can beconfigured by the LTE in the related art. In the present embodiment, thefrequency configured to the LAA cell is described as the non-allocatedfrequency, but is not limited to this. In other words, the non-allocatedfrequency can be replaced with a frequency configured to the LAA cell.For example, the non-allocated frequency is a frequency which cannot beconfigured to the primary cell, and is a frequency which can beconfigured only to the secondary cell(s). For example, the non-allocatedfrequency includes a frequency shared with multiple operators. Forexample, the non-allocated frequency is a frequency which is configuredonly to a cell configured, assumed and/or processed differently from theprimary cell or secondary cell(s) of the related art.

The LAA cell may be a cell which uses a different method from the methodof the related art for structures of radio frames, physical signalsand/or physical channels according to LTE, and a communicationprocedure.

For example, in the LAA cell, prescribed signals and/or channelsconfigured (transmitted) by the primary cell and/or the secondary cells)are not configured (transmitted). The prescribed signals and/or channelsinclude the CRS, the DS, the PDCCH, the EPDCCH, the PDSCH, the PSS, theSSS, the PBCH, a PHICH, a PCFICH, the CSI-RS and/or an SIB, or the like.For example, the signals and/or the channels that are not configured inthe LAA cell are as follows. In addition, the signals and/or thechannels described below may be used in combination. Note that in thepresent embodiment, the signals and/or the channels that are notconfigured in the LAA cell may also be read as signals and/or channelswhose the transmissions from the LAA cell are not expected by theterminal.

(1) in the LAA cell, control information of a physical layer is nottransmitted on the PDCCH, but is transmitted only on the EPDCCH.

(2) In the LAA cell, the CRS, the DMRS, the URS, the PDCCH, the EPDCCHand/or the PDSCH are not transmitted in subframes which are activated(on-state) or all subframes, and the terminal does not assume thistransmission in all subframes.

(3) In the LAA cell, the terminal assumes transmission of the DSs, thePSSs and/or the SSSs in subframes which are activated (on-state).

(4) In the LAA cell, information of CRS mapping is announced to theterminal for each subframe, and the terminal assumes the CRS mappingbased on the information. For example, according to the assumption ofthe CRS mapping, the CRS is not mapped onto all resource elements of thecorresponding subframe. According to the assumption of the CRS mapping,the CRS is not mapped onto part of resource elements (e.g., all resourceelements in two head OFDM symbols) of the corresponding subframe.According to the assumption of the CRS mapping, the CRSs are mapped ontoall resource elements of the corresponding subframe. For example, theinformation of the CRS mapping is announced from the corresponding LAAcell or a cell different from the corresponding LAA cell. Theinformation of the CRS mapping is included in the DCI and is announcedon the PDCCH or the EPDCCH.

For example, in the LAA cell, the prescribed signals and/or channelswhich is not configured (transmitted) by the primary cell and/or thesecondary cell(s) is configured (transmitted).

For example, in the FAA cell, only downlink component carrier orsubframe is defined, and only downlink signal and/or channel aretransmitted. In other words, in the LAA cell, uplink component carrieror subframe is not defined, and uplink signal and/or channel is nottransmitted.

For example, in the LAA cell, a Downlink Control Information (DCI)format which can be supported is different from a DCI format which cansupport the primary cell and/or the secondary cell(s). The DCI formatwhich supports only the LAA cell is defined. The DCI format whichsupports the LAA cell includes control information which is only validfor the LAA cell.

The terminal device can recognize the LAA cell, based on a parameterprovided by the higher layer. For example, the terminal device canrecognize a cell (band) in the related art or the LAA cell (LAA band),based on a parameter indicative of the center frequency of the componentcarrier. In this case, information about the center frequency isassociated with the type of the cell (band).

For example, in the LAA cell, the assumption of the signals and/orchannels is different from the secondary cells in the related art.

First, the assumption of the signals and/or channels in the secondarycells of the related art will be described. A terminal that satisfiespart or all of the following conditions assumes that the PSS, the SSS,the PBCH, the CRS, the PCFICH, the PDSCH, the PDCCH, the EPDCCH, thePHICH, the DMRS and/or the CSI-RS may not be transmitted by thesecondary cell except transmission of the DS. The terminal assumes thatthe DS is always transmitted by the secondary cell. The assumptioncontinues to a subframe in which an activation command (a command foractivation) is received by the terminal in the secondary cell at acertain carrier frequency

(1) The terminal supports a configuration (parameter) associated withthe DS.

(2) RRM measurements based on the DS is configured to the terminal inthe secondary cell.

(3) The secondary cell is deactivated (deactivated state).

(4) Reception of the MBMS by a higher layer is not configured to theterminal in the secondary cell.

Furthermore, in a case that the secondary cell is activated (activatedstate), the terminal assumes that the PSS, the SSS, the PBCH, the CRS,the PCFICH, the PDSCH, the PDCCH, the EPDCCH, the PHICH, the DMRS and/orthe CSI-RS are transmitted by the secondary cell in a configuredprescribed subframe or all subframes.

Next, an example of the assumption of the signals and/or channels in theLAA cell will be described. A terminal that satisfies part or all of thefollowing conditions assumes that the PSS, the SSS, the PBCH, the CRS,the PCFICH, the PDSCH, the PDCCH, the EPDCCH, the PHICH, the DMRS and/orthe CSI-RS may not be transmitted together with transmission of the DSby the LAA cell. The assumption continues to a subframe in which anactivation command (a command for activation)) is received by theterminal in the secondary cell at a certain carrier frequency.

(1) The terminal supports a configuration (parameter) associated withthe DS.

(2) RRM measurements based on the DS is configured to the terminal inthe LAA

(3) The LAA cell is deactivated (deactivated state).

(4) Reception of the. MBMS by a higher layer is not configured to theterminal in the LAA cell.

Furthermore, another example of the assumption of the signals and/orchannels in the LAA cell will be described. In a case that the LAA cellis deactivated (deactivated state), the assumption of the signals and/orchannels in the LAA cell is the same as the assumption of the signalsand/or channels in the secondary cells in the related art. In a casethat the LAA cell is activated (activated state), the assumption of thesignals and/or channels in the LAA cell is different from the assumptionof the signals and/or channels in the secondary cells in the relatedart. In a case that, for example, the LAA cell is activated (activatedstate), the terminal assumes that the LAA cell may not transmit the PSS,the SSS, the PBCH, the CRS, the PCFICH, the PDSCH, the PDCCH, theEPDCCH, the PHICH, the DMRS and/or the CSI-RS except a prescribedsubframe configured to the LAA cell. Details will be described below.

Furthermore, the description has been given of a case that CCA isperformed on one subframe, but a time (period) for performing CCA is notlimited to this. The period for performing CCA may vary per LAA cell,per CCA timing, or per execution of CCA. For example, CCA is performedat a time based on a prescribed time slot (a time interval or a timedomain). This prescribed time slot may be defined or configured based ona time obtained by dividing one subframe by the prescribed number. Theprescribed time slot may be determined or configured by the prescribednumber of subframes.

Furthermore, in the present embodiment, a field size in the time domainsuch as a time (time slot) for performing CCA or a time in which thechannel and/or signal are transmitted (can be transmitted) in a certainsubframe can be expressed by using a prescribed time unit. For example,the field size in the time domain is expressed by some time units Ts. Tsis 1/(15000×2048) seconds. For example, one subframe time is 30720×Ts(one millisecond). For example, one ICCA slot length or defer period is1044×Ts (approximately 33.98 microseconds) or 1045×Ts (approximately34.02 microseconds). For example, one ECCA slot length is 276×Ts(approximately 8.984 microseconds) or 277×Ts (approximately 9.017microseconds). For example, one ECCA slot length is 307×Ts(approximately 9.993 microseconds) or 308×Ts (approximately 10.03microseconds).

Furthermore, whether the LAA cell can transmit the channel and/or signal(including the reservation signal) from an intermediate symbol in acertain subframe may be configured for the terminal or the LAA cell. Forexample, information indicating whether such transmission is possible inthe configuration on the LAA cell is configured to the terminal by theRRC signaling. The terminal switches processing associated withreception (monitoring, recognition, and decoding) at the LAA cell basedon the information.

Furthermore, subframes in which symbols can be transmitted from anintermediate symbol (also including subframes in which symbols up to theintermediate symbol can be transmitted) may be all subframes in LAAcell. Furthermore, subframes in which symbols can be transmitted fromthe intermediate symbol may be subframes defined in advance for the LAAcell or configured subframes.

Furthermore, subframes in which symbols can be transmitted from theintermediate symbol (also including subframes in which symbols up to theintermediate symbol can be transmitted) can be configured, announced ordetermined based on an UpLink/DownLink configuration (UL/DLconfiguration) according to TDD. For example, such subframes aresubframes announced (designated) as special subframes by the UL/DLconfiguration. Each of the special subframes in the LAA cell is asubframe including at least one of the three fields, a Downlink PilotTime Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot Time Slot(UpPTS). The configuration on the special subframe in the LAA cell maybe configured or announced by the RRC signaling or PDCCH or EPDCCHsignaling. This configuration configures a length in time of at leastone of the DwPTS, the GP and the UpPTS. Furthermore, this configurationis index information indicating candidates of the predetermined lengthin time. Furthermore, for this configuration, the same length in time asthe DwPTS, the GP and the UpPTS used for the special subframeconfiguration configured to the TDD cells in the related art can beused. In other words, the length in time in which transmission ispossible in a certain subframe is determined based on one of the DwPTS,the GP and the UpPTS.

Further, in the present embodiment, the reservation signal may be asignal that can be received by a LAA cell different from the LAA cellthat transmits the reservation signal. For example, the LAA celldifferent from the LAA cell that transmits the reservation signal is theLAA cell (neighboring LAA cell) neighboring to the LAA cell thattransmits the reservation signal. For example, the reservation signalincludes information of a transmission state (use state) of a prescribedsubframe and/or symbol in the LAA cell. In a case that the LAA celldifferent from the LAA cell that transmits a certain reservation signalreceives the reservation signal, the LAA cell having received thereservation signal recognizes the transmission state of the prescribedsubframe and/or symbol, based on the reservation signal, and performsscheduling according to the state.

Furthermore, the LAA cell having received the reservation signal mayperform LBT before transmitting a channel and/or signal. This LTB isperformed based on the received reservation signal. For example, duringthis LBT, the channels and/or the signals transmitted (assumed to betransmitted) from the LAA cell having transmitted the reservation signalare taken into consideration, scheduling including resource allocationand MCS selection is performed.

Furthermore, in a case that the LAA cell having received the reservationsignal performs scheduling of transmitting the channels and/or signalsbased on the reservation signal, it is possible to announce informationof such scheduling to one or more LAA cells including the LAA cellhaving transmitted this reservation signal according to a prescribedmethod. For example, the prescribed method is a method for transmittingthe prescribed channel and/or signal including the reservation signal.Furthermore, for example, the prescribed method is a method forperforming announcement via a backhaul such as an X2 interface.

Furthermore, according to carrier aggregation and/or dual connectivity,a terminal of the related art can configure up to five serving cells.However, the terminal according to the present embodiment can extend amaximum number of serving cells that can be configured. In other words,the terminal according to the present embodiment can configure more thanfive serving cells. For example, the terminal according to the presentembodiment can configure up to 16 or 32 serving cells. For example, themore than five serving cells configured by the terminal according to thepresent embodiment include the LAA cell. Furthermore, all of the morethan five serving cells configured by the terminal according to thepresent embodiment may be the LAA cell.

Furthermore, in a case that the more than five serving cells can beconfigured, a configuration on part of the serving cells may bedifferent from the configuration of the serving cells in the related art(i.e., the secondary cell(s) in the related art). For example,differences of this configuration are as follows. The configurationsdescribed below may be used in combination.

(1) To the terminal, up to five serving cells in the related art areconfigured, and up to 11 or 27 serving cells different from servingcells in the related art are configured. In other words, to theterminal, in addition to a primary cell of the related art, up to foursecondary cells of the related art are configured, and up to 11 or 27secondary cells different from the secondary cells of the related artare configured.

(2) The configuration on the serving cells (secondary cells)) differentfrom the serving cells of the related art includes configurations on anLAA cell. For example, to the terminal, in addition to the primary cellin the related art, up to four secondary cells that do not include theconfiguration on the LAA cell are configured, and up to 11 or 27secondary cells different from the secondary cells in the related artare configured.

Furthermore, in a case that the more than five serving cells can beconfigured, the base station (including the LAA cell) and/or theterminal can perform different processing or assumption compared to thecase that up to five serving cells are configured. For example,differences of the processing and assumption are as follows. Theprocessing or the assumption described below may be used in combination.

(1) Even in the case that the more than five serving cells areconfigured, the terminal assumes that the PDCCH, the EPDCCH and/or thePDSCH are simultaneously transmitted (received) from the five servingcells at maximum. Consequently, the terminal can use the same method asthe method of the related art, for reception of the PDCCH, the EPDCCHand/or the PDSCH and transmission of HARQ-ACK for the PDSCH.

(2) In the case that the more than five serving cells are configured, acombination (group) of cells for bundling of HARQ-ACKs for the PDSCHs inthese serving cells are configured to the terminal. For example, allserving cells, all secondary cells, all LAA cells or all secondary cellsdifferent from the secondary cells in the related art includeinformation (configuration) on bundling of HARQ-ACKs between the servingcells. For example, the information of the bundling of HARQ-ACKs betweenthe serving cells is an identifier (an index or an ID) for performingthe bundling. For example, the bundling is performed on the HARQ-ACKsover cells having the same identifier to be bundled. This bundling isperformed according to a logical AND operation for the target HARQ-ACKs.Furthermore, the maximum number of identifiers to be bundled can befive. Furthermore, the maximum number of identifiers to be bundled canbe five including the number of cells that does not perform bundling. Inother words, the number of groups to perform bundling over the servingcells can be five at maximum. Consequently, the terminal can use thesame method as the method of the related art, for reception of thePDCCH, the EPDCCH and/or the PDSCH and transmission of HARQ-ACK for thePDSCH.

(3) In the case that the more than five serving cells are configured, acombination (group) of cells for multiplexing of HARQ-ACKs for thePDSCHs in these serving cells are configured to the terminal. In thecase that the combination (group) of the cells for multiplexing of theHARQ-ACKs for the PDSCHs is configured, the multiplexed HARQ-ACKs aretransmitted on the PUCCH or the PUSCH based on the group. The maximumnumber of serving cells to be multiplexed is defined or configured foreach group. The maximum number is defined or configured based on themaximum number of serving cells configured to the terminal. For example,the maximum number is the same as the maximum number of serving cellsconfigured to the terminal, or half the maximum number of serving cellsconfigured to the terminal. Furthermore, the maximum number of PUCCHs tobe simultaneously transmitted is defined or configured based on themaximum number of serving cells to he multiplexed in each group and themaximum number of serving cells configured to the terminal.

In other words, the number of configured first serving cells (i.e., theprimary cell and/or the secondary cell(s)) is a prescribed number (i.e.,five) or less. A total of the configured first serving cells and secondserving cell (i.e., LAA cell) exceeds the prescribed number.

Next, terminal capability associated with LAA will be described. Theterminal announces (transmits) information (terminal capability) oncapability of the terminal to the base station by the RRC signaling,based on a command from the base station. The terminal capability of acertain function (feature) is announced (transmitted) in a case that thefunction (feature) is supported, and is not announced (transmitted) in acase that the function (feature) is not supported. Furthermore, theterminal capability of the certain function (feature) may be informationindicating whether testing and/or mounting this function (feature) hasbeen finished. For example, the terminal capability according to thepresent embodiment is as follows. The terminal capability describedbelow may be used in combination.

(1) The terminal capability associated with support of the LAA cell, andthe terminal capability associated with support of a configuration ofmore than five serving cells are independently defined. For example, theterminal that supports the LAA cell supports the configuration of themore than five serving cells. In other words, the terminal that does notsupport the configuration of the more than five serving cells does notsupport the LAA cell. In this case, the terminal that supports theconfiguration of the more than five serving cells may or may not supportthe LAA cell.

(2) The terminal capability associated with support of the LAA cell, andthe terminal capability associated with support of a configuration ofmore than five serving cells are independently defined. For example, theterminal that supports the configuration of the more than five servingcells supports the LAA cell. In other words, the terminal that does notsupport the LAA cell does not support the configuration of the more thanfive serving cells. In this case, the terminal that supports the LAAcell may or may not support the configuration of the more than fiveserving cells.

(3) The terminal capability associated with downlink in the LAA cell,and the terminal capability associated with uplink in the LAA cell areindependently defined. For example, the terminal that supports theuplink in the LAA cell supports the downlink in the LAA cell. In otherwords, the terminal that does not support the downlink in the LAA celldoes not support the uplink in the LAA cell. In this case, the terminalthat supports the downlink in the LAA cell may or may not support theuplink in the LAA cell.

(4) The terminal capability associated with support of the LAA cellincludes support of a transmission mode configured only to the LAA cell.

(5) The terminal capability associated with the downlink according tothe configuration of the more than five serving cells, and the terminalcapability associated with the uplink according to the configuration ofthe more than five serving cells serving cells are independentlydefined. For example, the terminal that supports the uplink according tothe configuration of the more than five serving cells supports thedownlink according to the configuration of the more than five servingcells. In other words, the terminal that does not support the downlinkaccording to the configuration of the more than five serving cells doesnot support the uplink according to the configuration of the more thanfive serving cells. In this case, the terminal that supports thedownlink according to the configuration of the more than five servingcells may or may not support the uplink according to the configurationof the more than five serving cells.

(6) Regarding the terminal capability according to the configuration ofthe more than five serving cells, terminal capability that supports aconfiguration of 16 downlink serving cells (component carriers) atmaximum, and terminal capability that supports a configuration of 32downlink serving cells at maximum are independently defined.

Furthermore, the terminal that supports the configuration of 16 downlinkserving cells at maximum supports the configuration of at least oneuplink serving cell. The terminal that supports the configuration of 32downlink serving cells at maximum supports the configuration of at leasttwo uplink serving cells. That is, the terminal that supports theconfiguration of 16 downlink serving cells at maximum may not supportthe configuration of two or more uplink serving cells.

(7) The terminal capability associated with the support of the LAA cellis announced based on a frequency (band) used by the LAA cell. In a casethat, for example, the terminal announces a supported frequency or afrequency combination, and the announced frequency or frequencycombination includes at least one frequency used by the LAA cell, theterminal implicitly announces that this terminal supports the LAA cell.In other words, in a case that the announced frequency or frequencycombination does not include the frequency used by the LAA cell at all,the terminal implicitly announces that this terminal does not supportthe LAA cell.

Furthermore, the present embodiment has described a case where the LAAcell transmits the PDCCH or the EPDCCH for announcing the DCI for thePDSCH transmitted from this LAA cell (i.e., a case of self scheduling),but is not limited to this. The method described in the presentembodiment is applicable also in a case that, for example, a servingcell different from the LAA cell transmits the PDCCH or the EPDCCH forannouncing the DCI for the PDSCH transmitted from the LAA cell (i.e., acase of cross carrier scheduling).

Furthermore, in the present embodiment, the information for recognizingthe symbols in which the channels and/or signals are transmitted may bebased on the symbols in which the channels and/or signals are nottransmitted. For example, this information is information indicating thelast symbol of the symbols in which the channels and/or signals are nottransmitted. Furthermore, the information for recognizing the symbols inwhich the channels and/or signals are transmitted may be determinedbased on other information or parameters.

Furthermore, in the present embodiment, the symbols in which thechannels and/or signals are transmitted may be independently configured(announced or defined) to the channels and/or signals. In other words,the information for recognizing the symbols in which the channels and/orsignals are transmitted, and the announcement method of the informationcan be independently configured (announced or defined) to the channelsand/or signals. For example, the information for recognizing the symbolsin which the channels and/or signals are transmitted, and theannouncement method of the information may be independently configured(announced or defined) for the PDSCH and the EPDCCH.

Furthermore, in the present embodiment, symbols/subframes in which thechannels and/or signals are not transmitted (cannot be transmitted) maybe symbols/subframes in which the channels and/or signals are notassumed to be transmitted (be able to be transmitted) from a viewpointof the terminal, That is, the terminal can regard that the LAA cell doesnot transmit the channels and/or signals in the symbols/subframes.

Furthermore, in the present embodiment, the symbols/subframes in whichthe channels and/or signals are transmitted (can be transmitted) may besymbols/subframes in which the channels and/or signals may be assumed tobe transmitted from the viewpoint of the terminal. In other words, theterminal can regard that the LAA cell may or may not transmit thechannels and/or signals in the symbols/subframes.

Furthermore, in the present embodiment, the symbols/subframes in whichthe channels and/or signals are transmitted (can be transmitted) may besymbols/subframes in which the channels and/or signals are assumed to besurely transmitted from the viewpoint of the terminal. That is, theterminal can regard that the LAA cell surely transmits the channelsand/or signals in the symbols/subframes.

Next, an example of a configuration of a downlink reference signal inthe LAA cell will be described.

FIG. 5 is a diagram illustrating an example of the configuration of thedownlink reference signal. By way of example, the CRSs can be mapped toREs R0 to R3. R0 denotes examples of the REs on which the CRS of antennaport 0 is mapped, R1 denotes examples of the REs on which the CRS ofantenna port 1 is mapped, R2 denotes examples of the REs on which theCRS of antenna port 2 is mapped, and R3 denotes examples of the REs onwhich the CRS of antenna port 3 is mapped. Note that the CRSs may beshifted, for mapping, in the frequency direction according to aparameter associated with the cell identity. Specifically, an index kfor which the RE specifics mapping is increased based on a value ofN^(cell) _(ID) mod 6. Here, N^(cell) _(ID) denotes the value of thephysical cell identity. The DMRSs can be mapped to REs D1 and D2. D1denotes examples of the REs on which the DMRSs of antenna ports 7, 8,11, 13 are mapped, and D2 denotes examples of the REs on which the DMRSsof antenna ports 9, 10, 12, 14 are mapped. The CSI-RSs can be mapped toREs C1 to C4. C0 denotes examples of the REs on which the CSI-RSs ofantenna ports 15, 16 are mapped, C1 denotes examples of the REs on whichthe CSI-RSs of antenna ports 17, 18 are mapped, C2 denotes examples ofthe REs on which the CSI-RSs of antenna ports 19, 20 are mapped, and C3denotes examples of the REs on which the CSI-RSs of antenna ports 21, 22are mapped. Note that the CSI-RS may be mapped to the RE at OFDM symbol#5 or #6 in slot 0 and to the RE at OFDM symbol #1, #2, or #3 in slot 1.The REs on which the CSI-RS is mapped are indicated based on a parameterprovided by the higher layer.

Next, the relationship between a downlink transmission, an uplinktransmission, and LBT will be described.

FIG. 7 illustrates an example of the relationship between the intervalbetween a downlink transmission and an uplink transmission and types ofLBT on the time axis according to the present embodiment. In FIG. 7A, acase where the downlink transmission and the uplink transmission aresufficiently distant from each other on the time axis is illustrated. Inthe case where the downlink transmission and the uplink transmission aresufficiently distant from each other, for example, the interval betweenthe downlink transmission and the uplink transmission is at least onesubframe (1 millisecond). In such a case, there is no channel state(channel sensing result) correlation between the downlink transmissionand the uplink transmission, thus leading to the need to perform LBTinvolving sufficient carrier sensing on each transmission. Here, LBTperformed before the uplink transmission in FIG. 7A is referred to asfirst uplink LBT. In FIG. 7B, a case where the downlink transmission andthe uplink transmission are slightly distant from each other on the timeaxis is illustrated. In the case where the downlink transmission and theuplink transmission are slightly distant from each other, for example,the interval between the downlink transmission and the uplinktransmission corresponds to several symbols (several tens ofmicroseconds to several hundred microseconds). In such a case, CCAperformed before the downlink transmission may be considered to allowthe channel state (channel sensing result) to be also maintained beforethe uplink transmission. Thus, the terminal device may performsimplified CCA before transmitting an uplink signal. Here, LBT performedbefore the uplink transmission in FIG. 7B is referred to as seconduplink LBT. In FIG. 7C, a case where the downlink transmission and theuplink transmission are not substantially distant from each other on thetime axis is illustrated. In the case where the downlink transmissionand the uplink transmission are not substantially distant from eachother, for example, the interval between the downlink transmission andthe uplink transmission is several microseconds to several tens ofmicroseconds, such as 34 microseconds or 40 microseconds. In such acase, a channel is reserved for the uplink transmission by the downlinktransmission, and thus, the downlink transmission and the uplinktransmission may be regarded as one transmission burst. Thus, theterminal device may perform an uplink transmission without performingCCA. As in these examples, the uplink signal and/or channel can beefficiently transmitted also in the LAA cell by changing the LBTprocedure to be performed, according to the interval between thedownlink transmission and the uplink transmission.

The uplink transmission and the downlink transmission in FIG. 7 may beinterchanged with each other. In other words, downlink LBT may beomitted in a case that the uplink transmission and the downlinktransmission are not substantially distant from each other on the timeaxis.

Details of uplink LBT will be described below.

“Before performing an uplink transmission” or “before transmitting theuplink” means before an indicated timing (subframe) for the uplinktransmission.

In the first uplink LBT, the CCA check is performed multiple times usingthe backoff counter before the indicated timing for the uplinktransmission. The terminal device attempts the CCA check the number oftimes equal to a value in the backoff counter. In a case that all theCCA checks result in the determination that the channel is idle, theterminal device can acquire the right to access the channel to transmitthe uplink.

FIG. 8 illustrates an example of a procedure of the first uplink LBT. Ina case of detecting the uplink grant (S802) in the idle state (S801),the terminal device performs first CCA (S803). In the first CCA, first,the terminal device randomly generates a counter value N within therange from 0 to q-1 (S8031). Note that, in a case that a numerical valueassociated with the counter value N is indicated by the base stationdevice using the uplink grant, the terminal device uses the countervalue N based on the numerical value instead of generating a countervalue. Note that, in a case that the counter value does not become to 0in last LBT, with a value remaining in the counter, the terminal devicemay use the remaining counter value N instead of generating a countervalue N. Then, the terminal device starts CCA at a prescribed timing(S8032). The terminal device senses the channel (medium) during one CCAslot duration (S8033) to determine whether the channel is idle or busy(S8034). The terminal device decrements the counter value N by one(S8035) in a case of determining that the channel is idle, and returnsto the idle state (S801) instead of performing the uplink transmissionindicated by the uplink grant in a case of determining that the channelis busy. The terminal device then determines whether the counter valueis 0 (S8036), and in a case that the counter value is 0, acquires theright to access the channel and proceeds to a transmission operation(S804, S805). On the other hand, in a case that the counter value is not0, the terminal device senses the channel (medium) during one CCA slotduration again (S8033). Note that, in a case that the counter value N isgenerated, the value in the collision window q is updated to a valuebetween X and Y according to the channel state (S8037). In atransmission process, the terminal device determines whether to actuallyperform an uplink transmission at that timing (S804), and in a case ofdetermining to perform the uplink transmission, performs the uplinktransmission (S805). In a case of determining not to perform the uplinktransmission, the terminal device returns to the idle state (S801)instead of performing the uplink transmission indicated by the uplinkgrant.

The period of the first CCA may be preferably the same as the ECCAperiod in the downlink LBT.

Note that the ICCA may be performed before the first CCA as is the casewith the downlink LBT. However, even in a case that the ICCA results inthe determination that the channel is idle, the uplink is nottransmitted and the procedure proceeds to the first CCA operation.

In the second uplink LBT, the CCA check is performed only once beforethe instructed timing for the uplink transmission. The terminal deviceattempts the CCA check once. In a case of determining that the channelis idle as a result of the CCA check, the terminal device can acquirethe right to access the channel to transmit the uplink.

FIG. 9 illustrates an example of a procedure of the second uplink LBT.In a case of detecting the uplink grant (S902) in the idle state (S901),the terminal device performs second CCA (S903). In the second CCA, theterminal device starts CCA at a prescribed timing (S9031). The terminaldevice performs the CCA check during a CCA period to sense whether thechannel is idle or busy (S9032). In a case of determining that thechannel is idle as a result of the second CCA (S903), the base stationdevice acquires the right to access the channel and proceeds to atransmission operation. On the other hand, in a case of determining thatthe channel is busy as a result of the second CCA (S903), the terminaldevice returns to the idle state (S901) instead of performing the uplinktransmission indicated by the uplink grant. After proceeding to thetransmission operation, the terminal device determines whether toactually perform an uplink transmission at that timing (S904), and in acase of determining to perform the uplink transmission, the terminaldevice performs the uplink transmission (S905). In a case of determiningnot to perform the uplink transmission, the terminal device returns tothe idle state (S901) instead of performing the uplink transmissionindicated by the uplink grant.

The period of the second CCA may be preferably the same as the ICCAperiod in the downlink LBT.

Differences between the downlink LBT and the uplink LBT will be detailedbelow.

In the downlink the base station device performs the CCA check. On theother hand, in the uplink LBT, the terminal device performs the CCAcheck.

In the downlink LBT, LBT processing is started. in a case thatinformation (data, buffer, load, traffic) that needs to be transmittedhas occurred. On the other hand, for the uplink LBT, LBT processing isstarted in a case that an uplink transmission is indicated by the basestation device.

Note that the ICCA period of the downlink LBT may be preferably the sameas the period of the second CCA. Note that the ECCA period of thedownlink LBT may be preferably the same as the period of the first ICCA.

Next, specific examples are provided regarding switching between a caseof transmitting the uplink following the first uplink LBT and a case oftransmitting the uplink following the second uplink LBT or transmittingthe uplink with no uplink LBT,

By way of example, the procedure of the uplink LBT is switched based ona prescribed field included in the uplink grant (DCI format 0 or 4)indicating an uplink transmission.

The prescribed field refers to, for example, 1-bit informationspecifying the uplink LBT for the terminal device. In other words, theprescribed field refers to 1-bit information indicating whether thechannel has been successfully reserved (provided) in the subframeimmediately before the subframe indicated by the uplink grant. In a casethat a prescribed 1 bit is indicative of 0 (false, invalid, impossible),the terminal device performs the first uplink LBT before the uplinktransmission. In a case that the prescribed 1 bit is indicative of 1(true, valid, possible), the terminal device performs the second uplinkLBT before the uplink transmission or performs no uplink LBT.

Alternatively, the prescribed field refers to, for example, informationassociated with the counter value N used in the first uplink LBT. In acase that the prescribed field is 0 (invalid, impossible), the terminaldevice performs the second uplink LBT before the uplink transmission orperforms no uplink LBT. On the other hand, in a case that the prescribedfield contains a numerical value other than 0 (invalid, impossible), theterminal device generates a counter value N, based on the numericalvalue to perform the first uplink LBT.

The information associated with the counter value N is, for example, thecounter value N. The terminal device sets the value of the prescribedfield at the counter value N instead of generating a counter value N byitself.

Moreover, the information associated with the counter value N is, forexample, index information indicative of the configured counter value N.In a case that multiple candidates for the counter value N areconfigured for the terminal device by dedicated RRC and that the valuein the prescribed field has been acquired, the configured counter valueN corresponding to the information in the field is used.

Moreover, the information associated with the counter value N is, forexample, information associated with the collision window q. Multiplecandidates for the collision window q are configured for the terminaldevice by the dedicated RRC. In a case of acquiring the value in theprescribed field, the terminal device generates a counter value N byusing the configured value of the collision window q corresponding tothe information in the field. Note that the information associated withthe collision window q may be the value of the collision window q.

Note that the above-described examples may include switching between acase of transmitting the uplink following the second uplink LBT and acase of transmitting the uplink with no uplink LBT. Specifically, in acase that the prescribed 1 bit is indicative of 0, the terminal deviceperforms the second uplink LBT before the uplink transmission. On theother hand, in a case that the prescribed 1 bit is indicative of 1(true, valid, possible), the terminal device performs no uplink LBTbefore the uplink transmission.

The information in the prescribed field may be information indicatingwhether to generate a gap where LBT is to be performed. For example, ina case that 1 bit in the prescribed field is 1, the terminal devicetransmits the PUSCH with a gap of prescribed SC-FDMA symbols before thetransmission. In a case that the 1 bit in the prescribed field is 0, theterminal device transmits the PUSCH with no gap of prescribed SC-FDMAsymbols before the transmission. The prescribed SC-FDMA symbols are, forexample, several SC-FDMA symbols at the beginning or end of the subframeor a slot at the beginning or the end of the subframe.

Note that the prescribed field may be used along with any other field.For example, the procedure of the uplink LBT may be switched inaccordance with an SKS request field. Specifically, the terminal deviceperforms the second uplink LBT before the uplink transmission in a casethat the SRS request field is indicative of 0, and performs no uplinkLBT in a case that the SRS request field is indicative of 1. In a casethat the SRS request field is indicative of 0, nothing is transmitted inthe last one SC-FDMA symbol of the subframe. The terminal deviceperforms the second uplink LBT in the last one SC-FDMA symbol.

By way of example, the procedure of the uplink LBT is switched based ona prescribed field included in DCI different from an uplink grant.

The DCI different from the uplink grant refers to, for example, DCI fornotifying the terminal device whether the downlink transmission(transmission burst) has been performed in a subframe indicated in theDCI. Specifically, the subframe indicated in the DCI includes a subframeimmediately before the uplink transmission, and a prescribed field inthe DCI is information corresponding to a notification as to whether thedownlink transmission is to be performed. In a case that the prescribedfield in the DCI indicates that the downlink transmission is not to beperformed, the terminal device performs the first uplink LBT before theuplink transmission. On the other hand, in a case that the prescribedfield in the DCI indicates that the downlink transmission is to beperformed, the terminal device performs the second uplink LBT before theuplink transmission or performs no uplink LBT.

The information notified in the DCI different from the uplink grant is,for example, the length of the downlink transmission. The information isindicative of the beginning and/or end of the downlink transmission.Predefinition or pre-configuration of the length of the downlinktransmission allows the terminal device to recognize the length of thedownlink transmission, based only on the information about the beginningor end of the downlink transmission. As an example, in a case that thelength corresponds to one subframe and that the information in the DCIindicates that the downlink transmission starts at the beginning of aprescribed subframe, the terminal device recognizes that the downlinktransmission is to be performed in the one indicated subframe.

Moreover, the DCI different from the uplink grant may be preferablymapped in the non-LAA cell. Specifically, the DCI is mapped in thecommon search space present in the primary cell or the primary secondarycell, and one piece of DCI allows notification of informationcorresponding to multiple serving cells.

Furthermore, the DCI different from the uplink grant is scrambled withdedicated RNTI different from C-RNTI (RNTI for downlink transmissionnotification only, B-RNTI). The RNTI for downlink transmissionnotification only may be preferably configured individually for multipleterminal devices but may be configured with a value common to theterminal devices.

Moreover, the DCI different from the uplink grant, for example, has thesame format size as that of DCI format 1 C used for very small-scalescheduling for one PDSCH codeword, notification of an MCCH change, orTDD reconfiguration. Alternatively, the DCI, for example, has the sameformat size as that of DCI format 3 or DCI format 3 A used to transmit aTPC command for the PUCCH or the PUSCH.

Note that the DCI different from the uplink grant may correspond to anotification as to whether the uplink transmission (transmission burst)has been performed in a subframe indicated in the DCI.

Note that the above-described examples may include switching between acase of transmitting the uplink following the second uplink LBT and acase of transmitting the uplink with no uplink LBT. Specifically, in acase that the prescribed field in the DCI indicates that the downlinktransmission is not to be performed, the terminal device performs thesecond uplink LBT before the uplink transmission. On the other hand, ina case that the prescribed field in the DCI indicates that the downlinktransmission is to be performed, the terminal device performs no uplinkLBT before the uplink transmission.

By way of example, the procedure of the uplink LBT is switched accordingto the type of uplink channel or signal scheduled to be transmitted.

For example, the terminal device performs the first uplink LBT before atransmission of the PUSCH. The terminal device performs the seconduplink LBT before the PRACH or performs no uplink LBT.

For example, the terminal device performs the first uplink LBT before atransmission of the SRS with the PUSCH. The terminal device performs thesecond uplink LBT before the SRS without the PUSCH or performs no uplinkLBT.

By way of example, the procedure of the uplink LBT is switched dependingon whether a transmission of a downlink signal or channel from a cell towhich the terminal device is connected has been detected before theterminal device transmits the uplink.

For example, a comparison between the received power of the CRS and athreshold is used as a reference for detection of a transmission of adownlink signal or channel from the cell to which the terminal device isconnected. In a case that the terminal device determines that thereceived power of an RE on which the CRS of antenna port 0 (or antennaport 1, 2, 3) is mapped is smaller than a prescribed threshold in thesubframe immediately before the subframe for the uplink transmission,the terminal device performs the first uplink LBT before the uplinktransmission. On the other hand, in a case that the terminal devicedetermines that the received power of the RE on which the CRS of antennaport 0 (or antenna port 1, 2, 3) is mapped exceeds the prescribedthreshold in the subframe immediately before the subframe for the uplinktransmission, the terminal device performs the second uplink LBT beforethe uplink transmission or performs no uplink LBT.

For example, whether the reservation signal has been successfullydetected is used as the reference for detection of a transmission of thedownlink signal or channel from the cell to which the terminal device isconnected. In a case that the length of the downlink transmission ispredefined or pre-configured and that the terminal device hassuccessfully detected the reservation signal, whether the downlinktransmission is to be performed in the subframe immediately before thesubframe for the uplink transmission can be determined based on the timeof the detection of the reservation signal (subframe, symbol, RE, Ts)and the length of the reservation signal. In a case of determining thatthe downlink transmission is not to be performed in the subframeimmediately before the subframe for the uplink transmission, theterminal device performs the first uplink LBT before the uplinktransmission. On the other hand, in a case of determining that thedownlink transmission is to be performed in the subframe immediatelybefore the subframe for the uplink transmission, the terminal deviceperforms the second uplink LBT before the uplink transmission orperforms no uplink LBT. A reference as to whether the terminal devicehas successfully detected the reservation signal is, for example, acomparison between the received power of the RE to which the reservationsignal is assigned and a prescribed threshold.

For example, whether the PDCCH or the EPDCCH has successfully beendetected is used as the reference for detection of a transmission of thedownlink signal or channel from the cell to which the terminal device isconnected. In a case that the PDCCH or the EPDCCH has successfully beendecoded in the subframe immediately before the subframe for the uplinktransmission, the terminal device can recognize that the subframe isreserved by the terminal device as a downlink subframe. In other words,in a case that the PDCCH or the EPDCCH has successfully been decoded inthe subframe immediately before the subframe for the uplinktransmission, the terminal device performs the first uplink LBT beforethe uplink transmission. On the other hand, in a case that the decodingof the PDCCH or the EPDCCH fails in the subframe immediately before thesubframe for the uplink transmission, the terminal device performs thesecond uplink LBT before the uplink transmission or performs no uplinkLBT.

For example, whether the PDSCH has successfully been detected is used asthe reference for detection of a transmission of the downlink signal orchannel from the cell to which the terminal device is connected. In acase that the PDSCH has successfully been decoded in the subframeimmediately before the subframe for the uplink transmission, theterminal device can recognize that the subframe is reserved by the basestation device as a downlink subframe. In other words, in a case thatthe PDSCH has successfully been decoded in the subframe immediatelybefore the subframe for the uplink transmission, the terminal deviceperforms the first uplink LBT before the uplink transmission. On theother hand, in a case that the decoding of the PDSCH fails in thesubframe immediately before the subframe for the uplink transmission,the terminal device performs the second uplink LBT before the uplinktransmission or performs no uplink LBT.

For example, whether the DMRS has successfully been detected is used asthe reference for detection of a transmission of the downlink signal orchannel from the cell to which the terminal device is connected. In acase that the DMRS has successfully been detected in the subframeimmediately before the subframe for the uplink transmission, theterminal device can recognize that the subframe is reserved by the basestation device as a downlink subframe. In other words, in a case thatthe DMRS has successfully been decoded in the subframe immediatelybefore the subframe for the uplink transmission, the terminal deviceperforms the first uplink LBT before the uplink transmission. On theother hand, in a case that the DMRS has successfully been detected inthe subframe immediately before the subframe for the uplinktransmission, the terminal device performs the second uplink LBT beforethe uplink transmission or performs no uplink LBT. The reference as towhether the terminal device has successfully detected the reservationsignal is, for example, a comparison between the received power of an REto which the DMRS is assigned and a prescribed threshold. In otherwords, the reference is a comparison between the received power ofantenna port 7 or 9 and the prescribed threshold.

By way of example, the procedure of the uplink LBT is switched dependingon whether the terminal device has transmitted any uplink signal orchannel before transmitting the uplink.

For example, in a case that the terminal device has transmitted thePUSCH in the subframe immediately before the subframe for the uplinktransmission, the transmission can be performed without LBT in thissubframe because the channel has successfully been reserved for thesubframe as an uplink subframe. In other words, in a case that theterminal device has not transmitted the PUSCH in the subframeimmediately before the subframe for the uplink transmission, theterminal device performs the first uplink LBT or the second uplink LBTbefore the uplink transmission. On the other hand, in a case that theterminal device has transmitted the PUSCH in the subframe immediatelybefore the subframe for the uplink transmission, the terminal deviceperforms no uplink LBT.

For example, in a case that the terminal device has transmitted the SRSin the subframe immediately before the subframe for the uplinktransmission, the transmission can be performed without LBT because thechannel has successfully been reserved for the subframe as an uplinksubframe. In other words, in a case that the terminal device has nottransmitted the SRS in the subframe immediately before the subframe forthe uplink transmission, the terminal device performs the first uplinkLBT or the second uplink LBT before the uplink transmission. On theother hand, in a case of having transmitted the SRS in the subframeimmediately before the subframe for the uplink transmission, theterminal device performs no uplink LBT.

For example, in a case that the terminal device has transmitted thePRACH in the subframe immediately before the subframe for the uplinktransmission, the transmission can be performed in this subframe withoutLBT because the channel has been successfully reserved for the subframeas an uplink subframe. In other words, in a case that the terminaldevice has not transmitted the PRACH in the subframe immediately beforethe subframe for the uplink transmission, the terminal device performsthe first uplink LBT or the second uplink LBT before the uplinktransmission. On the other hand, in a case of having transmitted thePRACH in the subframe immediately before the subframe for the uplinktransmission, the terminal device performs no uplink LBT.

By way of example, the procedure of the uplink LBT is switched accordingto the configuration provided by the higher layer.

The configuration provided by the higher layer refers to, for example,configuration information specifying the procedure of the uplink LBT. Ina case that a configuration specifying the first uplink LBT is providedfor the terminal device, the terminal device performs the first uplinkLBT before an uplink transmission in the LAA cell for the terminaldevice. In a case that a configuration specifying the second uplink LBTis provided for the terminal device, the terminal device performs thesecond uplink LBT before an uplink transmission in the LAA cell for theterminal device. In a case that a configuration specifying that nouplink LBT is performed for the terminal device is provided, theterminal device performs no uplink LBT before performing the uplinktransmission in the LAA cell.

The configuration provided by the higher layer refers to, for example, aconfiguration for cross carrier scheduling for the LAA cell. In a casethat the cross carrier scheduling is configured for the LAA cell, theterminal device performs the first uplink LBT. In a case that selfscheduling is configured for the LAA cell (in other words, in a casethat the cross carrier scheduling is not configured for the LAA cell),the terminal device performs the second uplink LBT or performs no uplinkLBT. In other words, in a case that the PDCCH or the EPDCCH in theuplink grant for scheduling of the uplink transmission for the LAA cellis configured to be monitored for a cell other than the LAA cell, theterminal device performs the first uplink LBT before the uplinktransmission. On the other hand, in a case that the PDCCH or the EPDCCHin the uplink grant for scheduling of the uplink transmission for theLAA cell is not configured to be monitored for other than the LAA cell,the terminal device performs the second uplink LBT before the uplinktransmission or performs no uplink LBT.

The cross carrier scheduling may be configured for each of the downlinkgrant and the uplink grant. In that case, the above-described examplesof switching are regarded as switching as to whether the uplink grant isconfigured as the cross carrier scheduling.

The configuration provided by the higher layer refers to, for example,configuration of information indicative of a nation(s) where the LAAcell is operated. In a case that the information is indicative of aparticular nation(s) (for example, Japan or the Europe), the terminaldevice performs the first uplink LBT before the uplink transmission forthe LAA cell. On the other hand, in a case that the information isindicative of a country other than the particular nation(s) (forexample, the U.S. or China), the terminal device performs the seconduplink LBT before the uplink transmission for the LAA cell or performsno uplink LBT. The information indicative of the nation(s) where the LAAcell is operated is, for example, Public Land Mobile Network (PLMN). ThePLMN is an identifier indicative of a country and an operator. The PLMNis included in the SIB1 and notified to the terminal device. Note thatthe procedure of the uplink LBT may be switched according to theoperating band in addition to the information about the nation(s) wherethe LAA cell is operated. The information indicative of the operatingband can be identified in information about the center frequency of thecarrier (EARFCN value) configured by the higher layer.

The particular country is a country where LBT needs to be performed. Thecountry information and the capability of the terminal device may beassociated with each other. In other words, the terminal device may helinked with the particular nation(s) in such a manner that thecapability required for the terminal device is specified.

The configuration provided by the higher layer refers to, for example,configuration of the first uplink LBT. The procedure of the uplink LBTis switched depending on whether the first uplink LBT has beenconfigured for the terminal device. Specifically, in a case that thefirst uplink LBT has been configured by the higher layer, the terminaldevice performs the first uplink LBT before the uplink transmission forthe LAA cell. On the other hand, in a case that the first uplink LBT hasnot been configured by the higher layer, the terminal device performsthe second uplink LBT before the uplink transmission for the LAA cell orperforms no uplink LBT. The configuration of the first uplink LBTincludes, for example, information about the range X and Y fordetermination of the collision window q, a CCA slot length, a CCAthreshold, and the like.

Note that the procedure of the uplink LBT may be switched depending onwhether the second uplink LBT has been configured for the terminaldevice. Specifically, in a case that the second uplink LBT has beenconfigured by the higher layer, the terminal device performs the firstuplink LBT before the uplink transmission for the LAA cell. On the otherhand, in a case that the second uplink LBT has been configured by thehigher layer, the terminal device performs the second uplink LBT beforethe uplink transmission for the LAA cell. The configuration of thesecond uplink LBT includes, for example, the value of the collisionwindow q, the CCA slot length, the CCA threshold, and the like.

The configuration of the first uplink LBT and the configuration of thesecond uplink LBT may be preferably specific to each cell. Note that onepiece of configuration information may be configured commonly for allthe cells configured as serving cells. This is not applicable to non-LAAcells configured as serving cells.

Note that the switching may be performed based on a combination ofmultiple configurations provided by the higher layer. In a specificexample, in a case that the cross carrier scheduling is not configuredfor the LAA cell and that notification that the nation(s) where the LAAcell is operated is the particular nation(s) has been provided, theterminal device performs the second uplink LBT before the uplinktransmission for the LAA cell or performs no uplink LBT. In a case thatthe cross carrier scheduling is configured for the LAA cell and thatnotification that the nation(s) where the LAA cell is operated is otherthan the particular nation(s) has been provided, the terminal deviceperforms the first uplink LBT before the uplink transmission for the LAAcell.

Moreover, the switching may be performed in a case of combining multipleones of the above-described examples. In a specific example, in a casethat the self scheduling is configured for the LAA cell and that aprescribed field included in the uplink grant indicating the uplinktransmission indicates that the first LBT is to be performed, theterminal device performs the first uplink LBT before the uplinktransmission for the LAA cell. Otherwise the terminal device performsthe second uplink LBT before the uplink transmission for the LAA cell orperforms no uplink LBT.

Note that the parameter may be switched depending on the above-describedexamples. In a specific example, in a case that the terminal deviceperforms the first uplink LBT but the self scheduling is configured forthe LAA cell, a value configured by the higher layer (RRC) is applied tothe collision window q, and in a case that the cross carrier schedulingis configured for the LAA cell, the collision window q is updated ateach transmission opportunity based on the value configured by thehigher layer (RRC).

Note that the above-described examples may include switching between acase of transmitting the uplink following the second uplink LBT and acase of transmitting the uplink with no uplink LBT. In other words, in acase that the PDCCH or the EPDCCH in the uplink grant for scheduling ofthe uplink transmission for the LAA cell is configured to be monitoredfor a cell other than the LAA cell, the terminal device performs thesecond uplink LBT before the uplink transmission. On the other hand, ina case that the PDCCH or the EPDCCH in the uplink grant for schedulingof the uplink transmission for the LAA cell is not configured to bemonitored for a cell other than the LAA cell, the terminal deviceperforms no uplink LBT before the uplink transmission.

FIG. 10 illustrates an example of frequency multiplexing of the PUSCH inthe LAA cell. In the LAA cell, PUSCH resources are not contiguouslyallocated but are allocated at intervals of several subcarriers in thefrequency direction. The PUSCH is allocated among different terminaldevices in an interlaced manner such that subcarriers are nested. InFIG. 10, the PUSCH is allocated at intervals of three subcarriers, andthe PUSCH for three terminal devices is allocated in such a manner as tobe interlaced for each subcarrier. This allows the terminal devices toutilize the entire bandwidth with a few resources.

To allow frequency multiplexing or spatial multiplexing among multipleterminal devices in the LAA cell by using the same subframes (timeresources), transmission timings for the terminal devices need to beadjusted in such a manner that uplink channels and/or uplink signalsfrom the respective terminal devices are simultaneously received by thebase station device. Furthermore, in the LAA cell, the uplink LBT isperformed before the uplink transmission. In a case that LBT isperformed based on the counter value N, the number of attempts toperform CCA and the time needed for LBT vary according to the countervalue N. The relationship between start timings for the uplinktransmission and the uplink LBT will be described below.

FIG. 11 illustrates an example of the relationship between the starttimings for the uplink transmission and the uplink LBT. FIG. 11 is basedon operations in accordance with the procedure of the uplink LBT in FIG.8. The base station device notifies each terminal device of the timing(subframe) for the uplink transmission. The timing for the uplinktransmission is implicitly notified, for example, based on a subframe inwhich the uplink grant is received. The terminal device independentlygenerates a counter value N. The terminal device estimates the time whenthe uplink LBT is completed from the counter value N and the CCA periodto determine the LBT start timing. That is, the terminal device cancalculate the start timing tor the uplink LBT, based on the start timingfor the uplink transmission and the number of the first CCAs (countervalue N). In other words, the CCA for the uplink transmission starts(counter value N×CCA period) microseconds before the beginning of theuplink subframe for the terminal device.

In a case of determining that the channel is busy as a result of theCCA, the terminal device does not perform the uplink transmission at theindicated timing for the uplink transmission. At this time, the countervalue N is not discarded and is taken over by the next uplink LBT. Inother words, in a case that any counter value N remains in the counter,no counter value N is generated. Note that the counter value N may bediscarded and may not be taken over by the next uplink LBT depending onthe type of the DCI format or a particular parameter. For example, in acase of receiving information indicative of the first transmissionthrough a parameter indicative of new data (new data indicator), theterminal device discards the counter value N and does not take over thecounter value N to the next uplink LBT. Moreover, the counter value Nmay be linked with the HARQ process. In other words, the counter value Nfor the uplink LBT for the PUSCH is independent among different HARQprocesses.

Note that the uplink transmission may be performed in the middle of theuplink subframe. At that time, the CCA for the uplink transmissionstarts (counter value N×CCA period) microseconds before the beginning ofthe uplink transmission that the terminal device is indicated toperform.

Note that the initial CCA may be performed in the uplink LBT. In thatcase, the CCA for the uplink transmission starts (initial CCAperiod+counter value N+CCA period) microseconds before the beginning ofthe uplink subframe in which the terminal device is indicated to performthe uplink transmission.

Note that, in a case that time is needed to switch from a receiver to atransmitter, the start timing for the uplink LBT is determined with theswitching time taken into account. In other words, the CCA for theuplink transmission starts (counter value N×CCA period+time needed toswitch from the receiver to the transmitter) microseconds before thebeginning of the uplink subframe in which the terminal device isindicated to perform the uplink transmission.

Note that the start timing of CCA for the uplink transmission may becalculated based on the downlink radio frame (downlink subframe). Inother words, the CCA for the uplink transmission starts (counter valueN×CCA period+uplink-downlink frame timing adjustment time) microsecondsbefore the beginning of the downlink subframe corresponding to theuplink subframe in which the terminal device is indicated to perform theuplink transmission. Here, the uplink-downlink frame timing adjustmenttime is (N_(Ta)+N_(TA) _(_) _(offset))×T_(s), N_(TA) is a terminaldevice-specific parameter having a value from 0 to 20512 to adjust theuplink transmission timing, and N_(TA) _(_) _(offset) is a frameconfiguration type-specific parameter for adjustment of the uplinktransmission timing.

Here, in the LAA cell, a value that can be taken by N_(TA) may belimited. In other words, in the LAA cell, the maximum value of N_(TA) issmaller than 20512.

FIG. 12 illustrates an example of the relationship between the starttimings for the uplink transmission and the uplink LBT. FIG. 12 is basedon operations in accordance with the procedure of the uplink LBT in FIG.8. The base station device notifies each terminal device of the starttiming for the uplink LBT and information associated with the countervalue N. The start timing for the uplink LBT is implicitly notified, forexample, based on the subframe in which the uplink grant is received.The terminal device can recognize the start timing for the uplinktransmission, based on the start timing for the uplink LBT and thecounter value N. That is, the terminal device can calculate the starttiming for the uplink transmission, based on the start timing for theuplink LBT and the number of the first CCAs (counter value N). In otherwords, the uplink transmission starts (counter value N×CCA period)microseconds after the beginning of an uplink subframe in which theterminal device is indicated to perform CCA. Here, the same countervalue N is configured for all the terminal devices to be multiplexed.

The information associated with the counter value N is, for example, thecounter value N. In a case of being notified of the counter value N, theterminal device performs the uplink LBT by using the counter value N.

Moreover, the information associated with the counter value N is, forexample, a seed of random number used to generate the counter value N.The terminal device generates the counter value N by using the notifiedvalue and another parameter. Such another parameter is, for example, anaccumulated value of the HARQ-ACK for the PUSCH, the cell ID, a subframenumber, a system frame number, or the like.

The terminal device having determined that the channel is busy as aresult of the CCA does not perform the uplink transmission at theindicated timing for the uplink transmission. At this time, the countervalue N is discarded and is not taken over to the next uplink LBT.

Note that the initial CCA may be performed in the uplink LBT. In thatcase, the uplink transmission starts (initial CCA period+counter valueN×CCA period) microseconds after the beginning of an uplink subframe inwhich the terminal device is indicated to perform CCA.

Note that, in a case that time is needed to switch from the receiver tothe transmitter, the start timing for the uplink LBT is determined withthe switching time taken into account. In other words, the uplinktransmission starts (counter value N×CCA period+time needed to switchfrom the receiver to the transmitter) microseconds after the beginningof an uplink subframe in which the terminal device is indicated toperform CCA.

Note that the uplink transmission may be calculated based on thedownlink radio frame (downlink subframe). In other words, the uplinktransmission starts (counter value N×CCA period−uplink-downlink frametiming adjustment time) microseconds after the beginning of the downlinksubframe corresponding to the uplink subframe in which the terminaldevice is indicated to perform the CCA. Here, the uplink-downlink frametiming adjustment time is (N_(TA)+N_(TA) _(_) _(offset))×T_(s), N_(TA)is a terminal device-specific parameter having a value from 0 to 20512to adjust the uplink transmission timing, and N_(TA) _(_) _(offset) is aframe configuration type-specific parameter for adjustment of the uplinktransmission timing.

FIG. 13 illustrates an example of the relationship between the starttimings for the uplink transmission and the uplink LBT. FIG. 13 is basedon operations in accordance with the procedure of the uplink LBT in FIG.9. The base station device notifies each terminal device of the timing(subframe) for the uplink transmission. The timing for the uplinktransmission is implicitly notified, for example, based on a subframe inwhich the uplink grant is received. The terminal device determines thetime when the uplink LBT is completed based on the CCA period todetermine the LBT start timing. In other words, the CCA for the uplinktransmission starts (CCA period) microseconds before the beginning ofthe uplink subframe in which the terminal device is indicated to performthe uplink transmission.

Note that, instead of the timing for the uplink transmission, the starttiming for the uplink LBT may be notified. In that case, the terminaldevice can recognize the timing for the uplink transmission, based onthe CCA period. In other words, the CCA for the uplink transmissionstarts (CCA period) microseconds before the beginning of the uplinksubframe in which the terminal device is indicated to perform the uplinktransmission.

The terminal device having determined that the channel is busy as aresult of the CCA does not perform the uplink transmission at theindicated timing for the uplink transmission.

FIG. 14 illustrates an example of the relationship between the starttimings for the uplink transmission and the uplink LBT. FIG. 14 is basedon operations in accordance with the procedure of the uplink LBT in FIG.15 described below. The base station device notifies each terminaldevice of the timing (subframe) for the uplink transmission. The timingfor the uplink transmission is implicitly notified, for example, basedon a subframe in which the uplink grant is received. The terminal devicestarts the first CCA at the start timing for the first CCA. In a casethat the counter value N becomes 0, the terminal device waits until astart timing for third CCA. Then, the terminal device performs the thirdCCA at the start timing for the third CCA, and in a case that thechannel is idle during the entire CCA period, performs the uplinktransmission.

The start timing for the first CCA corresponds to, for example, thebeginning of the subframe before the uplink transmission. In otherwords, the first CCA for the uplink transmission starts at the beginningof the subframe closest to the beginning of the uplink transmission inwhich the terminal device is indicated to perform.

Alternatively, the start timing for the first CCA is determined, forexample, based on the collision window q for the terminal device. Inother words, the first CCA for the uplink transmission starts (collisionwindow q×CCA period) microseconds before the beginning of the uplinktransmission in which the terminal device is indicated to perform.

The third CCA for the uplink transmission starts (third CCA period)microseconds before the beginning of the uplink subframe in which theterminal device is indicated to perform the uplink transmission.

The third CCA period for the uplink transmission may be preferably thesame as the ICCA period.

FIG. 15 illustrates an example of the procedure of the uplink LBT. In acase of detecting the uplink grant (S1502) in the idle state (S1501),the terminal device performs the first CCA (S1503). In the first CCA,first, the terminal device randomly generates a counter value N withinthe range from 0 to q-1 (S15031). Note that, in a case that a numericalvalue associated with the counter value N is indicated by the basestation device using the uplink grant, the terminal device uses thecounter value N based on the numerical value instead of generating acounter value. Note that, in a case that the last LBT has not set thecounter value to 0, with a value remaining in the counter, the terminaldevice may use the remaining counter value N instead of generating acounter value N. Then, the terminal device starts CCA at the prescribedtiming (S15032). The terminal device senses the channel (medium) duringone CCA slot duration (S15033) to determine whether the channel is idleor busy (S15034). The terminal device decrements the counter value N byone (S15035) in a case of determining that the channel is idle, anddetermines whether a third CCA check timing has passed (S15038) in acase of determining that the channel is busy. In a case that the thirdcheck timing has not passed, the terminal device returns to the processof sensing the channel (medium) during one CCA slot duration (S15033).In a case that the third CCA check timing has passed, the terminaldevice returns to the idle state (S1501) instead of performing theuplink transmission indicated by the uplink grant. After the countervalue N is decremented by one, the terminal device determines whetherthe counter value is 0 (S15036), and in a case that the counter value is0, proceeds to the operation of the third CCA (S1504). On the otherhand, in a case that the counter value is not 0, the terminal devicesenses the channel (medium) during one CCA slot duration again (S15033).Note that the value in the collision window q obtained in a case thatthe counter value ⁻N is generated is updated to a value from X to Yaccording to the channel state (S15037). Then, in the third CCA (S1504),the terminal device waits until a timing when the third CCA starts(S15041), and senses the channel during the third CCA period (S15042).In a case of determining that the channel is busy as a result of thethird CCA, the terminal device returns to the idle state (S1501) insteadof performing the uplink transmission indicated by the uplink grant. Onthe other hand, in a case of determining that the channel is idle as aresult of the third CCA, the terminal device acquires the right toaccess the channel and proceeds to a transmission operation (S1505,S1506). In a transmission process, the terminal device determineswhether to actually perform the uplink transmission at that timing(S1505), and in a case of determining that the uplink transmission is tobe performed, performs the uplink transmission (S1506). In a case ofdetermining not to perform the uplink transmission, the terminal devicereturns to the idle state (S1501) instead of performing the uplinktransmission indicated by the uplink grant.

Note that the ICCA may be performed as is the case with the downlinkLBT. However, even in a case that the LCCA results in the determinationthat the channel is idle, the uplink is not transmitted and theprocedure proceeds to an ECCA operation.

The above-described constitution allows one subframe to be multiplexedto be transmitted and/or received in multiple terminal devices, withlong-term CCA checks performed by random number backoff.

Note that the LAA cell may be preferably operated in accordance with ahalf duplex scheme. The terminal device does not expect to receive, in asubframe in which an uplink transmission is being performed in one LAAcell, a downlink signal and/or channel from another LAA cell configuredas a serving cell. Specifically, the terminal device does not expect toreceive, in a subframe for which the PUSCH is scheduled in one LAA cellby DCI format 0/4, the PDCCH or the EPDCCH in all LAA cells configuredas serving cells. Furthermore, the terminal device performs, in thesubframe, no uplink LBT in the LAA cell configured as a serving cell.Alternatively, the terminal device may determine the result of theuplink LBT of the LAA cell configured as a serving cell to be busy inthe subframe. Moreover, the terminal device performs, in a subframe inwhich a downlink reception is being performed in one LAA cell, no uplinktransmission in another LAA cell configured as a serving cell. In aspecific example, the terminal device performs no uplink transmission insubframes configured as DMTC occasions. The terminal device does notexpect that the PUSCH is scheduled for subframes configured as DMTCoccasions. Moreover, in a serving cell operated as an LAA cell, theterminal device generates a guard period by avoiding reception of theend part of the downlink subframe immediately before the uplinksubframe. Alternatively, in a serving cell operated as an LAA cell, theterminal device generates a guard period by avoiding reception of thedownlink subframe immediately before the uplink subframe and receptionof the downlink subframe immediately after the uplink subframe.

Note that the uplink LBT may be performed during the guard period.

Part of the content described in the present embodiment is rephrased asfollows.

The terminal device includes a reception unit configured to receive aPDCCH, a transmission unit configured to transmit a PUSCH in a servingcell, and a CCA check unit configured to perform either first LBT forperforming a CCA check the number of times based on a random numberbefore a subframe for which a transmission of the PUSCH is indicated orsecond LBT for performing a CCA check only once. The terminal deviceswitches between the first LBT and the second LBT, based on a prescribedcondition.

Moreover, the information about the PDCCH is constituted by 1 bit. Thefirst LBT is performed before the subframe for which the transmission ofthe PUSCH is indicated in a case that the information about the PDCCH is1, and the second LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that the informationabout the PDCCH is 0.

Moreover, the first LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that a downlinktransmission burst is not detected in a subframe immediately before asubframe in which the PUSCH is transmitted, and the second LBT isperformed before the subframe for which the transmission of the PUSCH isindicated in a case that the downlink transmission burst is detected inthe subframe immediately before the subframe in which the PUSCH istransmitted.

Moreover, the first LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that the PDCCH isconfigured to be monitored in another serving cell different from theserving cell, and the second LBT is performed before the subframe forwhich the transmission of the PUSCH is indicated in a case that thePDCCH is not configured to be monitored in another serving celldifferent from the serving cell.

Moreover, the first LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that the PUSCH is nottransmitted in the subframe immediately before the subframe in Which thePUSCH is transmitted, and no LBT is performed before the subframe forwhich the transmission of the PUSCH is indicated in a case that thePUSCH is transmitted in the subframe immediately before the subframe inwhich the PUSCH is transmitted.

Furthermore, part of the content described in the present embodiment isrephrased as follows.

The terminal device includes a transmission unit configured to transmita PUSCH and a CCA check unit configured to perform LBT before a subframefor which a transmission of the PUSCH is indicated. The terminal devicedetermines an LBT start time, based on a PUSCH transmission start timeand a CCA slot length.

Moreover, in the LBT, a CCA check is performed the prescribed number oftimes, and the LBT start time is determined based on the PUSCHtransmission start time and the CCA slot length.

Moreover, the terminal device includes a reception unit configured toreceive a PDCCH. The number of the CCA checks is indicated by the PDCCH.

Note that the uplink LBT according to the present embodiment maysimilarly be applied to sidelink LBT for a sidelink transmission. Thesidelink transmission is used for device to device communication (D2D)between the terminal devices.

Note that, in a case that one or more configurations (LAA-Contig) whichare necessary for LAA communication for prescribed serving cell areconfigured to the terminal device 1, the prescribed serving cell may beregarded as the LAA cell. The configurations which are necessary for theLAA communication are, for example, a parameter associated with areservation signal, a parameter associated with RSSI measurement and aparameter associated with the second DS configuration.

In this regard, in a case that information (EARFCN value) on a centerfrequency associated with an LAA band for prescribed serving cell isconfigured to the terminal device 1, the cell of the frequency may beregarded as the LAA cell. The LAA bands (LAA operating band) refer to,for example, bands meeting one or more features of bands whose bandnumbers are 252 to 255, bands which are neither a TDD band nor an FDDband, bands which are defined by a 5 GHz band, and bands Which aredefined only by a 20 MHz bandwidth.

Note that the prescribed frequency may be preferably a frequency used bythe LAA cell. The prescribed frequency may be preferably a frequency ofcells which transmit the DSs based on LBT. The prescribed frequency maybe preferably a frequency of cells operated in an unlicensed band. Theprescribed frequency may be preferably a frequency of an operating bandassociated with a prescribed index of the operating band. The prescribedfrequency may be preferably a frequency of an operating band associatedwith an index of the operating band for LAA. The prescribed frequencymay be preferably an operating band associated with a prescribed indexof the operating band (E-UTRA operating band). For example, theoperating bands may be preferably managed by a table. An associatedindex is given to each operating band managed by the table. The index islinked to an associated uplink operating band, downlink operating bandand a duplex mode. Note that the uplink operating band is an operatingband used for reception at the base station device and transmission atthe terminal device. The downlink operating band is an operating bandused for transmission at the base station device and reception at theterminal device. Each of the uplink operating band and the downlinkoperating band may be preferably given by a lower limit frequency and anupper limit frequency (associated frequency band). The duplex mode maybe preferably given by TDD or FDD. The duplex mode in the LAA cell maybe other than TDD and FDD. For example, the duplex mode in the LAA cellmay be a transmission burst to be described below (optionally includingat least a downlink burst or an uplink burst).

In a case that, for example, the operating bands are managed by thetable, operating bands associated with an index “1” to an index “44” maybe preferably licensed bands (bands which are not LAA), and operatingbands associated with an index “252 to an index “255” may he preferablyunlicensed bands (LAA bands). Note that the uplink operating band maynot be preferably applied to the index “252” (n/a, not applicable). The5150 MHz to 5250 MHz may be preferably applied to the downlink operatingband. FDD may be preferably applied to the duplex mode. Furthermore, forthe index “253”, the uplink operating band may be preferably reserved(reserved to be used in future), and the downlink operating band may bepreferably reserved. FDD may he preferably applied to the duplex mode.Furthermore, for the index “254”, the uplink operating hand may hepreferably reserved (reserved to be used in future), and the downlinkoperating band may be preferably reserved. FDD may be preferably appliedto the duplex mode. Note that the uplink operating band may not bepreferably applied to the index “255” (n/a, not applicable). The 5725MHz to 5850 MHz may be preferably applied to the downlink operatingband. FDD may be preferably applied to the duplex mode. Note that 5150MHz to 5250 MHz and 5725 MHz to 5850 MHz may be preferably unlicensedbands (LAA hands). In other words, the prescribed frequencies describedabove may be preferably operating hands associated with the index “252”to the index “255”.

Moreover, although the description has been given in each of theabove-described embodiments by using the terms “primary cell” and “PScell”, these terms may not he necessarily used. For example, “primarycell” in each of the above-described embodiments may be referred to as“master cell”, and “PS cell” in each of the above-described embodimentsmay be referred to as “primary cell”.

A program running on each of the base station device 2 and the terminaldevice 1 according to the present invention may be a program (a programfor causing a computer to operate) that controls a Central ProcessingUnit (CPU) and the like in such a manner as to realize the functionsaccording to the above-described embodiments of the present invention.The information handled in these devices is temporarily stored in aRandom Access Memory (RAM) while being processed. Then, the informationis stored in various types of Read Only Memory (ROM) such as a Flash ROMand a Hard Disk Drive (HDD) and is read out by the CPU to be modified orrewritten, when necessary.

Moreover, the terminal device 1 and the base station device 2-1 or thebase station device 2-2 according to the above-described embodiments maybe partially realized by the computer. This configuration may beachieved by recording a program for enabling such controlfunctionalities on a computer-readable recording medium and causing acomputer system to read the program recorded on the recording medium forexecution.

Moreover, the “computer system” here is defined as a computer systembuilt into the terminal device 1 or the base station device 2-1 or thebase station device 2-2, and the computer system includes an OS andhardware components such as peripheral devices. Furthermore,“computer-readable recording medium” refers to a portable medium, suchas a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and astorage device, for example, a hard disk built into the computer system.

Moreover, the “computer-readable recording medium” may include a mediumthat dynamically retains the program for a short period of time, such asa communication line that is used to transmit the program over a networksuch as the Internet or over a communication circuit such as a telephonecircuit, and a medium that retains, in that case, the program for afixed period of time, such as a volatile memory within the computersystem that functions as a server or a client. Furthermore, the programmay be configured to enable some of the functionalities described above,and also may be configured to enable the functionalities described abovein combination with a program already recorded in the computer system.

Furthermore, the base station device 2-1 or base station device 2-2according to the above-described embodiments can be realized as anaggregation (a device group) constituted of a plurality of devices.Devices constituting the device group may be each equipped with some orall portions of each function or each functional block of the basestation device 2-1 or base station device 2-2 according to theabove-described embodiments. It is only required that the device groupitself include general functions or general functional blocks of thebase station device 2-1 or base station device 2-2. Furthermore, theterminal device 1 according to the above-described embodiment is capableof communicating with the base station device as the aggregation.

Furthermore, the base station device 2-1 or base station device 2-2according to the above-described embodiments may be an Evolved UniversalTerrestrial Radio Access Network (E-UTRAN). Furthermore, the basestation device 2-1 or base station device 2-2 according to theabove-described embodiments may have some or all portions of a functionof a higher node for an eNodeB.

Furthermore, sonic or all portions of each of the terminal device 1 andthe base station device 2-1 or base station device 2-2 according to theabove-described embodiments may be typically achieved as a Large-ScaleIntegration (LSI) that is an integrated circuit or may be realized as achip set. The functional blocks of each of the terminal device 1 and thebase station device 2-1 or base station device 2-2 may be individuallyrealized as a chip, or some or all of the functional blocks may beintegrated into a chip. Furthermore, the circuit integration techniqueis not limited to the LSI, and the integrated circuit may be achievedwith a dedicated circuit or a general-purpose processor. Furthermore,according to advances in semiconductor technologies, a circuitintegration technology that can replace LSI appears, it is also possibleto use an integrated circuit based on the technology.

Furthermore, according to the above-described embodiments, the cellularmobile station device is described as one example of a terminal deviceor a communication device, but the present invention is not limited tothis, and can be applied to a fixed-type electronic apparatus installedindoors or outdoors, or a stationary-type electronic apparatus, forexample, a terminal device or a communication device, such as anAudio-Video (AV) apparatus, a kitchen apparatus, a cleaning or washingmachine, an air-conditioning apparatus, office equipment, a vendingmachine, and other household apparatuses.

Heretofore, the embodiments of the present invention have been describedin detail with reference to the drawings, but the specific configurationis not limited to the embodiments, and includes, for example, designvariations that fall within the scope that does not depart, from thegist of the present invention. Furthermore, various modifications arepossible within the scope defined by claims, and embodiments that aremade by suitably combining technical measures disclosed in the differentembodiments are also included in the technical scope of the presentinvention. Furthermore, another configuration is also included such thatconstituent elements, each of which has been described in the aboveembodiments and achieve the same advantage, can be replaceable with eachother.

Supplement

(1) A terminal device according to an aspect of the present inventionincludes a reception unit configured to receive a PDCCH, a transmissionunit configured to transmit a PUSCH in a serving cell, and a CCA checkunit configured to perform either first LBT for performing a CCA checkthe number of times based on a random number before a subframe for whicha transmission of the PUSCH is indicated or second LBT for performing aCCA check only once. The terminal device switches between the first LBTand the second LBT, based on a prescribed condition.

(2) Moreover, in the terminal device according to an aspect of thepresent invention based on the above-described terminal device, theinformation about the PDCCH is constituted by 1 bit, the first LBT isperformed before the subframe for which the transmission of the PUSCH isindicated in a case that the information about the PDCCH is 1, and thesecond LBT is performed before the subframe for which the transmissionof the PUSCH is indicated in a case that the information about the PDCCHis 0.

(3) Moreover, in the terminal device according to an aspect of thepresent invention based on the above-described terminal device, thefirst LBT is performed before the subframe for which the transmission ofthe PUSCH is indicated in a case that a downlink transmission burst isnot detected in a subframe immediately before a subframe in which thePUSCH is transmitted, and the second LBT is performed before thesubframe for which the transmission of the PUSCH is indicated in a casethat the downlink transmission burst is detected in the subframeimmediately before the subframe in which the PUSCH is transmitted.

(4) Moreover, in the terminal device according to an aspect of thepresent invention based on the above-described terminal device, thefirst LBT is performed before the subframe for which the transmission ofthe PUSCH is indicated in a case that the PDCCH is configured to bemonitored in another serving cell different from the serving cell, andthe second LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that the PDCCH is notconfigured to be monitored in another serving cell different from theserving cell.

(5) Moreover, in the terminal device according to an aspect of thepresent invention based on the above-described terminal device, thefirst LBT is performed before the subframe for which the transmission ofthe PUSCH is indicated in a case that the PUSCH is not transmitted inthe subframe immediately before the subframe in which the PUSCH istransmitted, and no LBT is performed before the subframe for which thetransmission of the PUSCH is indicated in a case that the PUSCH istransmitted in the subframe immediately before the subframe in which thePUSCH is transmitted.

(6) Moreover, a base station device according to an aspect of thepresent invention is a base station device for communicating with aterminal device, the base station device including: a transmission unitconfigured to transmit a PDCCH; and a reception unit configured toreceive a PUSCH in a serving cell. The base station device is configuredto instruct the terminal device to switch between first LBT forperforming a CCA check the number of times based on a random numberbefore a subframe for which a transmission of the PUSCH is indicated,and second LBT for performing a CCA check only once.

(7) Moreover, in the base station device according to an aspect of thepresent invention based on the above-described base station device, theinformation about the PDCCH is constituted by 1 bit, the base stationdevice is configured to instruct the terminal device to perform thefirst LBT before the subframe for which the transmission of the PUSCH isindicated in a case that the information about the PDCCH is 1, and toperform the second LBT before the subframe for which the transmission ofthe PUSCH is indicated in a case that the information about the PDCCH is0.

(8) Moreover, in the base station device according to an aspect of thepresent invention based on the above-described base station device, thebase station device is configured to instruct the terminal device toperform the first LBT before the subframe for which the transmission ofthe PUSCH is indicated in a case that the PDCCH is configured to bemonitored in another serving cell different from the serving cell, andto perform the second LBT before the subframe for which the transmissionof the PUSCH is indicated in a case that the PDCCH is not configured tobe monitored in another serving cell different from the serving cell.

(9) Moreover, a communication method according to an aspect of thepresent invention is a communication method used by a terminal device,the communication method including: receiving a PDCCH; transmitting aPUSCH in a serving cell; and performing either first LBT for performinga CCA check a number of times based on a random number before a subframefor which a transmission of the PUSCH is indicated or second LBT forperforming a CCA check only once, the communication method switchesbetween the first LBT and the second LBT, based on a prescribedcondition.

(10) Moreover, a communication method according to an aspect of thepresent invention is a communication method used by a base stationdevice for communicating with a terminal device, the communicationmethod including: transmitting a PDCCH; and receiving a PUSCH in aserving cell. The communication method includes instructing the terminaldevice to switch between first LBT for performing a CCA check a numberof times based on a random number before a subframe for which atransmission of the PUSCH is indicated, and second LBT for performing aCCA check only once.

Cross-Reference to Related Application

The present application claims benefit of priority to JP 2015-154656filed on Aug. 5, 2015, the entire content of which is incorporatedherein by reference.

DESCRIPTION OF REFERENCE NUMERALS

301 Higher layer

302 Control unit

303 Codeword generation unit

304 Downlink sub frame generation unit

305 Downlink reference signal generation unit

306 OFDM signal transmission unit

307 Transmit antenna

308 Receive antenna

309 SC-FDMA signal reception unit

310 Uplink subframe processing unit

311 Uplink control information extraction unit

401 Receive antenna

402 OFDM signal reception unit

403 Downlink subframe processing unit

404 Downlink reference signal extraction unit

405 Transport block extraction unit

406 Control unit

407 Higher layer

408 Channel state measurement unit

409 Uplink subframe generation unit

410 Uplink control information generation unit

411 SC-FDMA signal transmission unit

412 Transmit antenna

The invention claimed is:
 1. A terminal device comprising: receptioncircuitry configured to receive a physical downlink control channelincluding a downlink control information (DCI) format; transmissioncircuitry configured to transmit a physical uplink shared channel(PUSCH) for a licensed assisted access cell scheduled by the DCI format;and clear channel assessment (CCA) check circuitry configured to performa listen before talk (LBT) procedure, the LBT procedure being aprocedure that senses a channel to determine whether the channel is idleor busy before transmission of the PUSCH, wherein the DCI formatincludes first information and second information, the first informationbeing 1 -bit information indicating either one type of a first type ofthe LBT procedure and a second type of the LBT procedure, the secondinformation associated with a window, in case of the 1 -bit informationindicating the first type of the LBT procedure, the CCA check circuitryis configured to determine a value of the window based on the secondinformation, generate a random value as a number of repetitions of CCAcheck with an upper bound based on the value of the window, and performthe repetitions of CCA check; and in case of the 1 -bit informationindicating the second type of the LBT procedure, the CCA check circuitryis configured to perform a single CCA check.
 2. A method for a terminaldevice, the method comprising: receiving a physical downlink controlchannel including a downlink control information (DCI) format;transmitting a physical uplink shared channel (PUSCH) for a licensedassisted access cell scheduled by the DCI format; and performing alisten before talk (LBT) procedure, the LBT procedure being a procedurethat senses a channel to determine whether the channel is idle or busybefore transmission of the PUSCH, wherein the DCI format includes firstinformation and second information, the first information being 1 -bitinformation indicating either one type of a first type of the LBTprocedure and a second type of the LBT procedure, the second informationassociated with a window, in case of the 1 -bit information indicatingthe first type of the LBT procedure, determining a value of the windowbased on the second information, generating a random value as a numberof repetitions of CCA check with an upper bound based on the value ofthe window, and performing the repetitions of CCA check; and in case ofthe 1 -bit information indicating the second type of the LBT procedure,performing a single CCA check.